At a conference in May at an upscale hotel in Beijing, China’s security-industrial complex offered its vision of the future. Companies big and small showed off facial-recognition security gates and systems that track cars around cities to local government officials, tech executives and investors.

Private companies see big potential in China’s surveillance build-out. China’s public security market was valued at more than $80 billion last year but could be worth even more as the country builds its capabilities, said Shen Xinyang, a former Google data scientist who is now chief technology officer of Eyecool, a start-up.

“Artificial intelligence for public security is actually still a very insignificant portion of the whole market,” he said, pointing out that most equipment currently in use was “nonintelligent.”

Many of these businesses are already providing data to the government.

Mr. Shen told the group that his company had surveillance systems at more than 20 airports and train stations, which had helped catch 1,000 criminals. Eyecool, he said, is also handing over two million facial images each day to a burgeoning big-data police system called Skynet.

At a building complex in Xiangyang, a facial-recognition system set up to let residents quickly through security gates adds to the police’s collection of photos of local residents, according to local Chinese Communist Party officials.

Wen Yangli, an executive at Number 1 Community, which makes the product, said the company is at work on other applications. One would detect when crowds of people are clashing. Another would allow police to use virtual maps of buildings to find out who lives where.

China’s surveillance companies are also looking to test the appetite for high-tech surveillance abroad. Yitu says it has been expanding overseas, with plans to increase business in regions like Southeast Asia and the Middle East.