Abstract: The experimental research was carried out on the energy output characteristics of insensitive RDX, RDX/Al and SEFAE in the explosion chamber and under water. Numerical simulation was conducted to study the internal blast loading of explosion chamber with flat end using TVD schemes. Strains on several typical positions on the wall of the chamber were measured under the different internal blast loadings. Results show that: (1) In the confined space RDX/Al and SEFAE have after-burning effect; (2) In the experiment condition the biggest blast loading appears at the joint point of flat end and cylinder; (3) Effect of blast loading by SEFAE on explosion chamber is the lowest and those by insensitive RDX and RDX/Al are the same. The compositions of frequencies of strains of different explosives are similar and there is a slight difference of intensity; (4) The structure of blast loading is not the main reason for strain growth.