The invention relates to a method for testing load-frequency adjusting characteristics of a speed control system of a power generating set of a gas turbine. The method is characterized in that a test module and a test control switch are added in control logic. The test method comprises the following steps: (a) adjusting the frequency of a simulation grid in the test module, and switching the testcontrol switch in the close state; (b) switching the test control switch to the open state, and making the response for increasing or lowering the power of the generating set; (c) recording the frequency change data of the generating set, substituting a parameter value into a simulation model, and comparing with the actual power change curve to verify the accuracy of the model; and (d) switching the test control switch to the close state after the test is finished, and recovering the grid frequency obtained by a rotation speed control system to the actual grid frequency. The method can carry out the test by switching the frequency, and can obviate the interference due to the frequency fluctuation of the grid to obtain stable characteristic data of the speed control system, thereby improving the parameter accuracy of the simulation model and the reliability for model verification of the speed control system of the gas turbine.