A semi-closed bomb experiment was designed to construct a system for evaluating the erosion performance of propellant according to actual requirements. A transient numerical simulation model was established based on the geometric dimensions of the erosion tube and the measured p-t curve. The relationship between the transient erosion rate model parameters and the total mass loss of erosion tube was established through the space-time distribution of wall temperature of the erosion tube. Based on the mass loss of the semi-closed bomb experiment， the parameters of erosion reaction were optimized by particle swarm algorithm. The results showed that both the temperature of the interface between the propellant gas and the erosion tube wall and the growth rate of melting depth decreased with the increase of erosion time. The 45^# steel and double base powder （Shuang-fang 3） were selected as the material sample and propellant sample. The optimized pre-factor and apparent activation energy values are 0.3403 s^-1 and 134.6 kJ∙mol^-1， respectively. At this time， the loss function is only 3.0×10^-6. Thus， the transient erosion rate model is a promising tool to evaluate the erosion status of the barrel weapon.