Molecular dynamics (MD) simulation was employed to investigate safety performance (sensitivity), thermal expansion and mechanical properties of solid propellant. The models of high energy multi-component systems with different sets of proportion were studied at different temperatures. It is found that the maximum bond lengths (L_max) of both O—N and N—N trigger bonds in the five-component system with the mass ratio of (PEG/NG/BTTN):AP:HMX＝2.5:3.5:2.3 are the longest among the four sets of the systems. Results show that the safety of the system having this proportion is relatively low. The L_max of each deflagrating component in the six-component system (PEG/NG/BTTN)/AP/HMX/Al increases monotonously with the increasing temperature, which agrees with the experimental fact that energy materials become more sensitive as the temperature increases. It is suggested that structure parameter L_max can also be used as a theoretical criterion of thermal or impact sensitivity to predict the relative safety of multi-component complicated systems. Based on the simulation results for the six-component system, thermal expansion coefficients at different temperatures are calculated and mechanical properties are obtained with the static method.