Abstract: In order to improve the performance of fuel breeding and core safety, new thorium molten salt reactor (TMSR) core was designed, which employs BeO as moderator and BeF₂-free fuel salt. Based on this design, steady state and transient safety characteristics of TMSR were preliminarily analyzed using multi-physics code. By the transient simulation for start-up, pump speed down/up, loss of heat sink and so forth, the temperature and power response were analyzed. The results indicate that the new designed TMSR has excellent safety performance under various operating conditions.