There is a lack of quantitative analysis methods in the thermal design stage of relay protection equipment. Thus temperature simulation analysis and life assessment of high heat loss components of the equipment are carried out. First, the structural characteristics and heat dissipation mechanism of relay protection equipment are analyzed, a refined modeling method for thermal simulation of chassis and board is proposed, and a finite element simulation model of typical relay protection equipment is established based on Icepak. Then by changing the parameters of the finite element model of the relay protection equipment, the operating temperature of the high heat loss components under different ambient temperatures and different heat dissipation measures is calculated, and the temperature change of the high heat loss components is quantitatively analyzed. From this a life assessment method of high heat loss components based on the temperature distribution characteristics of relay protection equipment and the Arrhenius equation is proposed. The influence of equipment operating environment temperature on the life and reliability of components is revealed. The temperature characteristics and life analysis results of components can provide data and a theoretical basis for thermal design and optimization of relay protection equipment.