The jet was flying between the cities of Kunming and Guangzhou on Monday when it nosedived into a mountainside with 132 people on board, all of whom were killed.
The cause of the disaster is not yet known.
"The second black box from China Eastern flight MU5735 was recovered on March 27," Xinhua news agency reported.
The plane was equipped with two flight recorders: one in the rear passenger cabin tracking flight data, and the other a cockpit voice recorder.
The latter was found on Wednesday and sent to Beijing for analysis, which is expected to take several more days.
The second black box contains data such as speed, altitude and heading.
With both now recovered, investigators should be able to begin to piece together what caused the plane to fall more than 6,000 metres (20,000 feet) in just over a minute.
Hundreds of people, including firefighters, doctors and investigators, remain at the scene of the tragedy recovering human remains and the wreckage of the plane.
The Chinese Civil Aviation Administration (CAAC) said on Saturday evening that all of the people on board the aircraft had died, and that it had confirmed almost all of their identities through DNA testing.
All 123 passengers and nine crew members were Chinese nationals.
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