The invention relates to a finite element simulation technology, and discloses a combined environmental stress simulation method which can analyze the stress distribution of a simulation model under acombined environment and make simulation results better conform to actual situations. The method comprises the steps that a, a geometric model is created, material parameters at different temperatures are defined, the model is segmented, and a grid is divided, and a finite element model is generated; b, heat-structural coupling prestress analysis conducted, wherein the temperature and the pressure load are applied to obtain comprehensive stress of thermal stress generated by high temperature and a static stress generated by a pressure load, and the comprehensive stress serves as prestress forsubsequent random vibration analysis; c, the prestress is loaded into the finite element model for modal analysis with prestress; d, vibration excitation is applied, random vibration analysis is carried out, and a random vibration stress result is obtained; e, a random vibration stress result, the thermal stress generated by the high temperature and a static stress result generated by the pressure load are superposed. The method is suitable for combined environmental stress simulation analysis.