Combustion synthesis was employed to fabricate a wear-resistant composite using reactions between Ti, Al, Fe3O4, B4C, and CrO3 powders on the steel plate. CaF2 was used to improve the fluidity and decrease the melting temperature of Al2O3. A large number of holes were found in the top of the composite with different contents of ceramic particles. To elucidate the relationship between the mass fraction of ceramic particles and porosity, the adiabatic temperatures of different combustion systems were calculated. The porosity and size distribution of the holes of samples with different ceramic particle contents were studied, and the distributions and compositions of the ceramic particles were analyzed. The compositions surrounding and inside the holes were studied, and the hardness of the composite was also tested. The results show that the formation of holes is associated with the vaporization of Al and Cr. The porosity increases with an increase in the ceramic particle contents which is the combined effect of the decreasing adiabatic temperature, the increasing nucleation rate, the increasing ceramic particle sizes, the increasing viscosity of the metal, and the wetting angle between the liquid and solid phase, while the composition of ceramic particles has little effect. The hardness values of all composites exceed 60 HRC.