It is mainly concerned the modification of Composition B to control exudation,restrain irreversible size growth,enhance mechanical properties and decrease sensitivity. A kind of modified Composition B was made with coated RDX by a kind of aromatic copolymer in this work. Experimental results show that the exudation percentage and the size growth percentage of modified Composition B could be decreased by 47.6% and 75% respectively,and in the mean time,the mechanical intensity could be increased by 2 times. The sensitivity could be decreased to a certain degree,compared to that of Composition B without modification.