Fault free performance of fluid control components used to control flow, pressure and direction of propellant and pressurant is essential for reliable performance of launch vehicle propulsion stages. Relief valves (RV) are safety devices used in pressurisation system that releases excess pressure during over pressurisation conditions. In cryogenic propulsion systems, the design of RV is complex due to change in working temperature of operating fluid from ambient to 80 K. The performance and dynamic characteristic of RV is a function of mechanical properties of valve elements, geometrical & functional parameters, gaseous thermo-physical properties, etc. A non-linear dynamic mathematical model of cryogenic pressure RV is required for predicting the performance of valves in specified working conditions w.r.t. initial transients, temperature effects, variation in input/output conditions. Also, the pressure difference from cracking till full opening of valve is very important for deciding design pressure of propellant tanks. The present study analyses a cryogenic pressure RV using mathematical model considering effects of back pressure and temperature in transient and steady state. The model is validated with lab experiments to a limited extent w.r.t. working environments. Later, the effect of various parameters including back pressure on RV’s performance is studied by simulations and some experiments.