2.5D SiCf/SiC composites were produced by a modified polymer infiltration and pyrolysis process. Fine Al and SiC powders were first infiltrated into large inter-bundle pores. During pyrolytic decomposition of the polymer, the active Al filler reacts with small carbon-bearing polymer fragments, and reactive nitrogen atmosphere to form new phases of carbide or nitride. The volume expansion compensates for polymer shrinkage to a certain degree. The microstructural evolution and mechanical performances were characterized. The result indicates that the addition of Al fillers has significant influence on the mechanical properties of the composites. For the composite with Al loading, a proportional-limit stress of 380 MPa and a maximum stress of 441 MPa are achieved.