China's manned submersible Jiaolong returned to its attendant ship at about 1:02 pm Saturday after placing a marker on the seabed.
The State Oceanic Administration (SOA) said in a statement that Saturday's mission, the last in a succession of four test dives that began on July 21, was a complete success.
The submersible took samples, tested its underwater acoustic communication set, and shot photos in the eastern Pacific, according to the administration.
The undersea activities further testified the function and stability of the undersea craft in deep sea, the statement said, without saying how deep the submersible went in the fourth dive.
In its previous three dives, Jiaolong reached a depth of 5,188 meters, according to the statement.
Ye Cong, Liu Kaizhou and Fu Wentao were the members of the three-man crew that completed the feat, which began at 4:26 am Saturday.
Jiaolong, named after a mythical sea dragon, was designed to reach a depth of 7,000 meters.
China is the fifth country to send a man 3,500 meters below sea level, following the United States, France, Russia and Japan.