The small modular reactor (SMR), which has the characteristics of modularization, integration, passive safety design and high inherent safety, is designed in Hainan Changjiang multi-use modular small reactor technology demonstration project. In order to demonstrate that the safety objective of the latest regulatory requirements, to support the review of new nuclear power projects, and to support the demonstration of the safety goal of “practically eliminating an early radioactive release or a large radioactive release”, the risk of a large radioactive release for SMR is evaluated. Through the analysis of key elements such as plant damage state, containment capacity analysis, containment event tree, fault tree, quantitative analysis and source term, the integrated internal event PSA model is established. It is assessed that the risk of large releases due to internal events is low, and the conditional containment failure probability is relatively small. The results prove the high safety and balanced design of SMR. An assessment was carried out for the release category that accounts for the large release, i.e., the containment bypass release category. The reasons for the high share of this release category are analyzed and sensitivity analyses are performed for its dominant sequences.