A drunken NYU teaching assistant crashed through three marble landings while trying to jump the stairs at an East Village building early Sunday — seriously injuring himself and leaving 40 partiers stranded on the roof, authorities said.

Boozed-up investment-banking student Tao Niu, 20, tumbled the equivalent of nearly two stories as he went smashing through the 1- to 2-inch-thick slabs at the apartment building on Second Avenue near East 10th Street, officials said.

“The guy jumped. He broke through a couple of landings,” said a source with the city’s Office of Emergency Management, which had video of the 1:30 a.m. stunt gone awry.

A friend who lives in the building said Niu, a student at NYU’s prestigious Stern School of Business, “was barely moving” after his fall.

“[He] was definitely a little intoxicated and probably stumbled down,” the friend said.

Dozens of people, mostly NYU students, were partying on the roof at the time.

Firefighters had to use ladders and buckets to get many of them down, officials said.

Some of the revelers took to the building’s fire escapes, but others refused, saying they appeared to be too unstable.

“The fire escape is not deemed to code,” one partygoer insisted. “When they were actually trying to get people off, some of the rings were breaking. So that’s why they were bucketing people.”

Partier Shauna Ashcroft, 22, said: “It was complete chaos. I heard a loud noise, and after that everyone started panicking.

“I’ve never been so scared in my entire life!” she said.

A former accounting professor described Niu as “one of the top students” in his class.

Friends said Niu is only about 150 pounds.

“They don’t handle pressure well,” one resident said of the landings. “This kid was like 5-foot-8!”

Authorities are continuing to investigate the cause of the collapse.

“I have no idea what kind of weight [the staircase is] supposed to sustain,” an OEM source said.

“But, obviously, it was not being used normally. It was jumped on by a grown man from 10 to 12 feet in the air.”

A friend of Niu said, “He has a couple things broken.

“But other than that, he’s very, very lucky,” the pal said.

Niu was in serious but stable condition at Bellevue Hospital. He suffered broken ribs and a fractured ankle, officials said.

A friend at the hospital said he was “doing OK, but sleepy.”

Niu’s LinkedIn page says he won first place in the JPMorgan IB Risk Case Competition in 2012.

He also worked as an intern in equity research for Wedbush Securities.

The building where he was injured was deemed still habitable after the incident. The landings have been replaced with planks and boards.

The building manager declined to comment on the incident Sunday.

Additional reporting by Kirstan Conley