Abstract: The peaceful utilization of nuclear energy is being closely concerned around the world. As one of the generation Ⅳ reactors, the proliferation resistance performance of the small modular thorium based MSR should be assessed since proliferation risk is one of the four indexes to evaluate the performance of the generation Ⅳ nuclear system. Accordingly, the multi-attribute utility analysis (MAUA) was used to compare the proliferation resistance of the small modular thorium based MSR based on three kinds of reprocessing modes and once-through PWR with quantified values from the viewpoint of attractiveness level, handling requirements, accessibility etc. The results show that the nuclear security measurement (NS) value of the small modular thorium based MSR is around 0.8 which is comparable to the once-through PWR and superior to the closed cycle CANDU. Furthermore, a preliminary improvement of proliferation performance was conducted based on the mode Ⅲ small modular thorium based MSR. Therefore, this work aims to apply the quantitative proliferation resistance evaluation method to study and optimize the nuclear fuel cycle, which can provide a scientific and reasonable reference for the decision-making of nuclear energy deployment.