Three floors of a 31-story building were affected by fire on Monday, but no one was injured.
Almost 100 firefighters arrived less than 20 minutes to control the fire, China News Service said.
The fire hit the No 6 building, a residential and commercial complex at JianWai SOHO in Chaoyang district. The cause of the blaze is still unknown, but there are theories ranging from a cigarette butt to a faulty air-conditioner.
Beibei, a shop assistant in her 20s who works in the building, said she smelt smoke and "felt scared".
"So I ran out off the building," she said.
"We've heard that the fire might be caused by an abandoned cigarette end."
Zhang Minwei, 46, who lives nearby, said the fire broke out at about 4 pm and affected three floors, from the 22nd to the 24th.
Zhang said he was told the fire was caused by an air-conditioner fixed to the outside wall of the 22nd floor.
"I heard a wire in the machine sparked and caused the fire," he said. "The fire, fanned by gusty winds, fed on lots of paper bags piled inside the building," he said.
Zhang said the property management company should take responsibility for the fire.
"They don't care about keeping the building safe, but focus on chasing profits."
Zhou Peng, a project manager at Pinnacle Realty Management International, the company managing the building, refused to comment.
A Chaoyang district fire fighting bureau official said the cause of the fire hadn't been determined.
More than 1,400 households occupy the complex.