In order to suppress the effects of stray light radiation on imaging for mid-infrared plane grating spectrometer system. First, the sources of stray light for spectrometer system were investigated, the baffle, vane and Lyot stop were designed. Then a new method of combining shutter barrier and stray light collector was proposed to solve the shortage of using normal light barrier to suppress the higher order diffraction stray light, and Solidworks and Tracepro softwares were used to model, analyze and compare the system. Finally, the sytem using an infrared thermopile array detector according to blackbody radiation theory was calculated and analyzed. Final analysis results show that the Point Sources Transmittance of the spectrometer can reach the level of 10-11, effective emissivity is 1.3%, two results show that the stray light suppression can meet the requirements.