Chinese student Ye Mengyuan, 16, survived the July 6 crash only to be run over by a fire truck while she was covered in firefighting foam, authorities have said.
The death "was a tragic accident that did not involve any violation of our criminal laws," San Mateo County District Attorney Steve Wagstaffe said in a news release.
Wagstaffe said he arrived at his decision after reviewing police, fire and other first responder reports, the coroner's investigation and numerous videos of events at the scene.
In all, 304 of the 307 people aboard the Boeing 777 survived the crash, although dozens of people were injured.
Ye and a friend were seated at the back of the plane that came in too low and too slow, clipping its landing gear and tail on a rocky seawall just short of the runway.
It was unclear how Ye got from the airplane to the spot where she died. Investigators believe she was down on the ground and not standing during the aftermath of the plane crash.
The cause of the crash is under investigation. The National Transportation Safety Board has said it did not find any mechanical problems with the plane during a preliminary review.
But the plane's pilots, as well as the airline, have raised the possibility that a key device that controls the Boeing 777's speed may have malfunctioned.
Ye and her close friend, 16-year-old Wang Linjia, who also died, were students at Jiangshan Middle School in Zhejiang, an affluent coastal province in eastern China, Chinese state media has reported. They were part of a group of students and teachers from the school who were heading to summer camp in Southern California.
The other victim, 15-year-old Liu Yipeng, later died at a hospital.