The invention discloses a large oil suspension cylinder dynamic performance testing method and system. The method comprises the following steps: multiple sets of high-frequency small-amplitude reciprocating loading tests and multiple sets of low-frequency large-amplitude reciprocating loading tests are performed on an oil suspension cylinder to obtain testing data of the oil suspension cylinder, wherein the testing data comprises a compression travel and a compression speed of the oil suspension cylinder and test output force; an oil suspension cylinder mathematical model is built according toa gas state equation, hydromechanics and thermodynamics principles; the oil suspension cylinder mathematical model is corrected according to the test data to obtain a corrected mathematical model; and compression travel-output force and compression speed-output force curves are obtained according to a present compression travel change curve of the oil suspension cylinder and the corrected mathematical model. The method can reduce requirements on a loading system acceleration by a traditional oil suspension cylinder dynamic performance testing method, can greatly reduce the testbed installed power, and meanwhile, can guarantee accuracy of suspension cylinder dynamic performance data.