Workers came to repair a malfunctioning elevator in the northern city of Xi’an on January 30, Beijing Youth Daily cited local authorities as saying.
The crew found the elevator stuck between the 10th and 11th floors, shouted to ask if anyone was there, and cut the power, it said.
The workers left for the week-long Lunar New Year holiday and did not return until March 1.
The government said the investigation found the death was due to a grave error by the maintenance company for not opening the car before cutting the power, and not verifying after the power was off whether there was anyone inside.
The deceased woman, 43, reportedly lived alone in building.
China is prone to safety accidents as regulations and standards are often flouted and enforcement is lax, sometimes due to corruption.
Police investigating the incident found no evidence of trauma and have ruled out homicide, Beijing Youth Daily said.
Last July, a woman was killed after she plunged through flooring over an escalator in a Chinese department store.
Security camera footage of the incident posted online showed a panel in the floor giving way as the woman stepped off the escalator. As she fell half-way through she pushed her son forward, and a nearby shop assistant dragged him to safety.