For the outside world, China’s film market can be full of surprises. This time, it caught Chinese audiences – and even one of its own filmmakers -- off guard.

China woke up on Friday to discover that local film authorities had submitted “Go Away, Mr. Tumor” – a crowd-pleasing romantic comedy that was big at the box office but light on gravitas and rave reviews– the country’s official entry in the Foreign Language Film Award category of the annual Academy Awards. Many had expected the honor to go to “Wolf Totem,” a highly touted film with big Chinese state backing and a prestigious French director.

The move even surprised the director of “Mr. Tumor,” Han Yan, who wrote on his verified Weibo social-media account Friday morning that he didn’t know about the decision until hours ago. The 31-year-old director, whose name wasn’t previously widely known in China, said he felt “extremely lucky” that his film was chosen.

“Go Away, Mr. Tumor” is a romance based on a popular online comic about a female cartoonist who fights cancer and falls in love with her doctor. It has grossed more than 510 million yuan so far since its release earlier this summer, and stars Bai Baihe of the 2011 surprise comedy hit “Love Is Not Blind” and the California-born heartthrob Daniel Wu.

Chinese local media had previously reported that the State Administration of Press, Publication, Radio, Film and Television had chosen “Wolf Totem” as China’s contender. That film was helmed by French director Jean Jacques Annaud, who won the Foreign Language Oscar in 1976, and is based on a bestselling and influential Chinese novel of the same name. It grossed nearly 700 million yuan in the local market.

Wang Weimin, producer of “Wolf Totem,” told China Real Time that the film failed to pass the Academy’s review because its director and the leading screenwriter, Alain Godard, are both French, instead of Chinese nationals. Mr. Wang said Chinese officials and his team previously understood this standard to be “flexible.”

Last year, China’s film authority submitted “The Nightingale,” another Sino-French co-production directed by French director Philippe Muyl, as its entry in the foreign-language category. The film, which was also regarded as a surprise choice last year, tells the story of a road trip taken by an old man and his spoiled granddaughter through the southern Chinese countryside.

“I respect the decision made by the Academy and I already felt honored that SAPPRFT chose this film to be the entry,” said Mr. Wang, referring to the top regulator. “’Mr. Tumor’ is a film with ‘positive energy’ and I wish it good luck.”

Academy officials and the Chinese regulator didn’t respond to requests for comment.

China has been longing for a Oscar statuette for years. It used to submit productions by the country’s most prominent directors. They include Zhang Yimou, whose films submitted include the 2002 martial arts epic “Hero,” and Feng Xiaogang, whose films include the 2012 sober famine story “Back to 1942.”

But so far the only Mandarin-language film to win a major award is Taiwan’s “Crouching Tiger, Hidden Dragon,” which in 2001 won the foreign-language category. “The Last Emperor,” which won Best Picture and other major awards in 1988, had some Mandarin but was mostly in English and was directed by Italy’s Bernardo Bertolucci.

The choice of “Mr. Tumor” drew criticism online in China. “I am not saying that the film is bad, but can such a chick flick really represent China? So disgraced!” said one Weibo user based in Beijing.

Industry figures told China Real Time that the Chinese regulator has only limited criteria for what it submits. Among them is that the film should be shown for commercial purposes for consecutive seven days in local theaters before October, and that the authority prefers productions that look at the positive aspects of society and people’s lives.

Liu Qingqing, deputy general manager of Wanda Pictures, which co-produced “Mr. Tumor,” said his company was approached by the regulators days earlier, and was given notice that this film was chosen “without explanation” on why.

Mr. Liu described “Mr. Tumor” as a quality film with commercial success. As to the film’s Oscar journey ahead, the company holds modest expectations. “We are already honored to be chosen as the national representative to the Oscars,” he said.

--Lilian Lin. Follow her on Twitter @LilianLinyigu.