Abstract: In order to improve the activity and combustion efficiency of aluminum powder,a mechanical ball milling method was used to prepare Al/C composite particles and the milling conditions were optimized. The results show that,when the carbon content is 30%,the ratio of balls mass to powder mass is 14,the rotating speed is 350 rad/s,hexane is used as an inert atmosphere and the milling time is 2 hours,the sizes of Al and C in the composite particles are 33.2 nm and 42.5 nm respectively,the relative effective activity can reach up to 70.33%. The effects of composite particles on the viscosity,mechanics,explosion heat,burning rate and other properties of composite propellant were studied respectively. The results suggest that composite particles can increase the viscosity of HTPB propellant,but the system is a typical shear thinning fluid. The more composite particles are added,the greater the degree of shear thinning will be. Therefore,the propellants containing composite particles can be formed with high quality by selecting appropriate addition amount and processing conditions. And particles will improve the mechanical strength of HTPB propellant. When the particles content increases from 0% to 30%,the average maximum tensile strength and fracture strength enhance from 0.37 MPa and 0.32 MPa to 0.75 MPa and 0.69 MPa respectively. In addition,composite particles can significantly improve the explosive heat and burning rate of the propellant. For example,taking 15% composite particles as the replacement amount,the explosive heat and burning rate can be increased by 9.91% and 48.27%,respectively,compared with the blank.