As the main coolant piping from the steam generator to the reactor pressure vessel, cold leg is an important part of the primary circuit. During a LOCA accident in the cold leg, the parameter sensitivity has a crucial influence for the containment response. PAREO program is used to analyze the sensitivity of the pressure response of HPR1000 containment. Quantitatively evaluated the influence of free volume, area of thermal components, spray flow rate and internal atmospheric temperature on the pressure and temperature of containment under the condition of LOCA. The results show that the area of thermal components is the most sensitive parameter to the pressure response process of containment. The research results could provide technical support for containment design, safety analysis and assessment.