To investigate the effect of additives on the impact sensitivity and power of Comp.B, modified Comp.B was prepared by adding 123 resin, polyester fibre and thermoplastic elastomer VP-401, respectively. Big-bill hammer impact sensivity test, Susan test and cylinder test of the samples were conducted. The changes in the impact sensitivitly and power of Comp.B were obtained. The effects of compressive elasticity and toughness on the impact sensitivity as well as content of additives on the power for modified Comp.B were discussed. Results show that by adding 1% 123 resin, the compressive elasticity and toughness of Comp.B can be obviously improved, and the height of the threshold of deflagration reaction is enhanced by 3 m, and the impact sensitivity is obviously reduced. The modified Comp.B with 123 resin still belongs to a kind of explosive with lower strength, the fragmentation of the explosive has occured in the process of plastic deformation occured with the shell within the time range of several hundred microseconds from the Susan projectile′s impact on the target to explosion of fragmentated explosive. The fragmentation degree of the explosive greatly affects the percentage of deflagration, i.e. the relative energy is released. Compared with the power capability of Comp.B, the power of Comp.B with 1% 123 resin is decreased by 4.6% and 1.24%, respectively at radial distance of 5 mm and 19 mm.