The assessment of fatigue life for landing gears is challenging due to the complexity of load conditions and the continuous variation of shock absorber travel (SAT). This paper focuses on the high-cycle fatigue (HCF) issue of the sliding tube (SL). Based on the whole geometric model of the main landing gear (MLG), the HCF is studied by considering the SAT under various fatigue load cases. Firstly, the method of unit load decomposition was explored based on MLG ground load spectrum. Then, a quasi-static finite element analysis model of the MLG was established using ANSYS Workbench to simulate stress response for 115 unit conditions under 5 different SAT. Finally, employing stress superposition method and nCode software, the fatigue life of SL structural in the MLG was analyzed. The results indicate that the minimum fatigue life of the SL is 49610 cycles, meeting the requirement of 48,000 cycles according to the design objective.