In order to meet the requirement of Extreme Ultraviolet (EUV) transmission grating spectrometer in terrestrial space, thermal and mechanical properties of 2000 l/mm X/EUV transmission grating was investigated by means of simulation method. The mechanistic model was established and its thermal and coupling properties were simulated using the method of finite element analysis. Moreover, the distributions of thermal field and thermal deformation were obtained based on transmission grating consisting of different materials with different thermal expansion coefficients. The results are shown that the surface deformation of transmission grating is 0.56 μm as well as the longitudinal deformation value is 71.5 nm (average value). Due to thermal deformation, the diffraction efficiency and precision of spectrograph decline. In terms of simulation results, the package and structure of grating were optimized for applications in solar EUV radiation spectroscopies.