Abstract: The transient thermal hydraulic characteristics of 49-2 Pool Type Low Temperature Heating Reactor were analyzed by RELAP5/MOD3.2 code under the beyond design basis accident (BDBA) of station blackout anticipated transient without scram (SBO-ATWS). The results show that 49-2 Pool Type Low Temperature Heating Reactor has the minus reactivity feedback effect. With the rising of the temperatures of the fuel and the coolant, the reactor can be subcritical by the effect of the minus reactivity feedback. And then, the residual heat of the core can be removed to the environment through the natural circulation. Therefore, it demonstrates the inherent safety of 49-2 Pool Type Low Temperature Heating Reactor when served as low temperature heating supply for the city.