When a rupture occurs in a reactor coolant system, the increase in pressure and temperature is not uniform across compartments, so that the transient after the accident generates different differential pressures in the compartments, and thus there is a pressure loading acting on the walls of the compartments, which has to be taken into account in the design of the walls of the compartments. By calculating each transient parameter of the compartment, it can support the design of compartment loads, improve the ability to cope with severe accidents in nuclear power plants, and provide a theoretical basis for the safe design of containment.. The pressure and temperature response of the compartments during the short time of pipe rupture is obtained by calculating the mass and energy exchange and distribution between several control bodies and the fluid state in the control bodies, and the two groups with larger mass and energy in the mass-energy release data, i.e., the single-end fracture of the inlet receiver of the waste heat discharge system and the single-end fracture of the inlet receiver of the annealing box, are selected for the back-of-the-envelope calculations. The results show that: after the accident, the temperature in the large space of the containment decreases and then increases, and the temperature in the rest of the compartments increases rapidly in 0s-0.8s, and then remains stable; the maximum relative temperature in the compartments in the case of single-end fracture of the inlet pipe of the waste heat discharge system can be up to 2.21, and the maximum relative temperature in the compartments in the case of single-end fracture of the annealing pump pipe can be up to 1.94; the pressure in the ruptured compartments is always higher than the other compartments; the pressure in the ruptured compartments is always higher than the other compartments. The pressure in the breach compartment is always the highest compared with other compartments, and the pressure difference between the breach compartment and other compartments reaches the peak in a short period of time, and then decreases slowly; the highest relative pressure difference in the compartment in the case of accidental single-end breakage of the inlet pipe of the waste heat discharge system can be up to 0.0391, and that in the case of accidental single-end breakage of the injection pump pipe can be up to 0.00186. The pressure loads on the wall of the compartment in the case of an accident of LOCA can be obtained. The pressure load of the compartment wall in the LOCA accident was obtained, which provides theoretical support for the protection of the structural integrity of the compartment wall after the accident.