A 16-year-old Chinese exchange student was walking to her Queens school Wednesday when she was suddenly, randomly slashed across the throat by a maniac wearing a surgical mask and white gloves, authorities and relatives said.

The Whitestone Academy 11th-grader had just stepped out the front door of her family’s home when the crazed man crept up behind her and pushed her to the ground at 8:20 a.m. at 147th Street and 13th Avenue in Whitestone, cops said.

“He came out of nowhere. She was walking to school with a bookbag,” said NYPD Chief of Detectives Robert Boyce.

The hooded madman — who was caught on a neighbor’s home surveillance video (above) — slashed the girl’s neck and face with a box cutter before dropping his weapon and fleeing, police said.

“Once he slashed her, he ran off. … It’s very disturbing,” Boyce said.

Neighbors and local workers said a homeless man known to have threatened passers-by in the past had been lurking around the area earlier in the morning. It was unclear whether he had anything to do with the attack, but police were questioning people about him and asking if they’d seen him.

“He’s been here since the summer,” a Walgreens employee said. “The way this man got in my face before, I thought he would hurt me.”

The injured girl, who told cops she didn’t know her attacker, stumbled back to her home after the attack drenched in blood and related to her aunt what had happened, the aunt said.

“This is terrible,” the aunt, the girl’s guardian, told The Post, declining to provide her and the victim’s names.

“She was on the way to school, only an 8-minute walk, when she was attacked. She was carrying a cup of hot chocolate.”

The girl was taken to LIJ Children’s Hospital, where she underwent surgery for gashes on her neck and left cheek, officials said.

“This could have been much worse. She could have died,” a hospital source said, adding that the victim will be scarred on her face for life. “She is going to be OK. She is not going to die. She got hurt.”

The victim’s aunt said the wounds were “so deep. There was so much blood. … We hope he gets caught.”

The girl moved to New York City from China in August, according to the aunt.

“She is a good student, a good girl. I cannot believe this happened to her, so close to the home. She doesn’t know the man,” she said.

A neighbor whose surveillance video captured the attack said, “When you look at the video, you see a slim tall man wearing a hoodie. You couldn’t really see his face.”

“He ran up to her from behind, grabbed her face and just started slashing her,” said the neighbor, who asked not to be named.

Assemblyman Ron Kim (D-Flushing), who stopped by the scene of the attack and visited the family at the hospital, said the Chinese community is concerned that the attack is a bias incident.

“In the last few months, there has been a pattern of attacks against Asian-Americans, especially with our own playwright David Henry Hwang,” he said.

“The family is obviously in shock. The entire community, when they see this, can imagine their own child going to school and being attacked out of the blue.”

He added that the victim is “recovering well,” but is “very traumatized.”

The attack has left neighbors on edge, knowing that the assailant is still on the loose.

“It’s concerning,” said Alyia Wallace, who is a mother. “You don’t know whether he is living around here, he could be hiding in someone’s yard. It is so random.”

The suspect was described as possibly being in his 20s and wearing a surgical mask, white gloves, and a gray hooded sweatshirt with black stripes on the sleeves.

Additional reporting by Natalie Musumeci