Effects of aluminum content and sintering temperature on microstructures of TiCp/Al master alloy were investigated. The DSC results showed that reaction temperatures of the Al-Ti-C system were influenced by aluminum content. The average grain size of TiCp in the master alloy was 0.5～1μm with 40wt% Al content at 750°C sintering temperature. TiCp/AZ91 composites were fabricated through remelting TiCp/Al master alloy in magnesium alloy. Microstructural characterization of the TiCp/AZ91 composites showed relatively uniform distribution of TiC particulates in the matrix material and the hardness of the composites was improved significantly.