The fatigue life of the coupler is crucial for ensuring the safety of heavy-haul railway transportation. Aiming at the problem of fatigue life evaluation of couplers of heavy-haul railway freight cars, This paper presents a study on the evaluation method of coupler fatigue life based on fatigue bench tests. The method for compiling fatigue test load spectrum and the quantitative evaluation index of fatigue life are proposed. Based on the measured load spectrum of coupler force of 20,000-ton marshalling heavy-haul train on typical heavy-haul freight typical lines in China, the decomposition of tensile and compressive loads and their influence on the fatigue damage of couplers were studied. The damage-equivalent fatigue test load spectrum was determined to be compiled by using the mixed tension - tension load spectrum. Considering the actual situation of the random position change of couplers in the train, the equivalent damage value for compiling the test load spectrum was determined using statistical methods. Based on the damage equivalence principle and the Goodman equation, and considering the influence of the average load, the load cycles at various levels were equivalently transformed into five different levels of load cycles, thus significantly shortening the test time and obtaining the accelerated test load spectrum. The 5-level coupler test load spectrum compiled in this paper achieves a balance between damage equivalence accuracy and test efficiency. Based on the test load spectrum, an accelerated fatigue test of the coupler is conducted. According to the fatigue test results and considering the actual service conditions of the coupler, a quantitative evaluation index for the fatigue life of couplers applicable to fatigue bench tests was proposed.