The invention relates to a cable testing method, especially to a load cycle heating method of a high-voltage alternating-current cable. According to the existing heating method for the alternating-current cable load cycle at the low voltage level, a test loop applies the same heating current as a simulated loop, so that the cable temperature of the test loop is higher than the highest operating temperature. The heating method comprises: obtaining a structural parameter and a material parameter of a cable; establishing equivalent heat circuit models of a test loop and a simulated loop; calculating a simulated loop steady-state current in a highest temperature state of a conductor; constructing a loss equivalent model; obtaining corresponding loss equivalent models of the simulated loop and the test loop; calculating an equivalent dielectric loss current in a steady state; and determining a heating current of the test loop. According to the heating method, the influence on temperature control equivalence of load cycle test and simulation loops by dielectric losses of the high-voltage cable are considered fully; and a phenomenon that the practical temperature of the test loop conductor is higher than that of the simulated loop can be avoided.