Abstract: Radioisotope thermoelectric generator (RTG) could supply power for various engineering applicated scenarios, including sea, terrestrial and space due to its long-life span, strong environment adaptability and maintenancefree. Among them, powering terrestrial equipment is one of the important applications for RTG. ²⁴¹AmO₂ can be utilized as a source of terrestrial RTG energy supply because of its long half-life, wide access and low dose rate. This article designs a 60-watt-class ²⁴¹AmO₂ RTG and calculates the output electrical performance and safety performance under different environment temperature in terrestrial based on ANSYS finite element analysis (FEA) software. The results show that the maximum output power and temperature distribution of RTG is clearly influence by the environment temperature. The RTG could provide output electrical power range from 66.0 to 75.7 W while the environment temperature is -60~50 ℃. The maximum of fuel and thermoelectric module hot junctions temperature are 789 ℃ and 717 ℃. The output electrical and safety performance meet the requirements of RTG design index.