Abstract: To evaluate the safety characteristics of pulsed reactor under LOCA (loss of coolant accident), an analytical model of LOCA is developed and an advanced code XPRLOCA with friendly interactive interface and real time simulation function is coded for simulating LOCA. The calculating results of LOCA for Xi'an pulsed reactor show that when the break is below lower grid plate and the break diameter is smaller than 26 mm, the reactor core is safe. Otherwise, the emergency core cooling system has to go into operation, the maximum temperature of fuel must be below 900 ℃ under the LOCA condition.