Abstract: The relations between infiltration depth of metal liquid to the capillary between particles and processing parameter have been derived by mathematic analysis for the vacuum infiltration process,i.e.　H=R2(Ρ1+2σcosθ/R)τη The heat resistant steel based composites containing WC, Ni coated Al₂O₃, Al₂O₃ particles have been gained with vacuum infiltration process, and the particles in matrix are well distributed. The effects of the wetting of metal liquid with particles and the sizes of particles on infiltration depth have been confirmed by experiments.