The invention relates to a bidirectional sealing performance test method of a mechanical vibrator. The test method comprises the following steps of: mounting the mechanical vibrator to be tested on a test cylinder, connecting an external leakage test device, increasing the pressure and temperature in a buffer tank and the test cylinder to predetermined values, and keeping temperature and pressure for a predetermined time to obtain the bubbling condition of a water tank; keeping pressure in the test cylinder unchanged, increasing pressure in an air inlet to a predetermined increase value, and keeping temperature and pressure for a predetermined time to obtain the change condition of the indicating value of a trace flowmeter; and synchronously releasing pressure of the test cylinder and the air inlet of the mechanical vibrator, removing the mechanical vibrator finishing the test, mounting the next equipment, and repeating the steps. The method provided by the invention has the advantages that: the nondestructive test of the tested mechanical vibrator is realized, repeated increase of temperature and pressure for the next test is avoided, the test cost is saved, the test efficiency is improved, and the system has reasonably designed entire structure and is safe and reliable.