The vacuum-free semi-solid stirring brazing process of SiCp/A356 composites was investigated. Under a certain stirring and brazing condition, the effects of the solid fraction in filler metal on the microstructure, bonded ratio and the tensile strength of bonded joints were investigated. Results show that with stirring the solid fraction of the semi-solid filler metal has a significant influence on the break of the substrate oxide film. And, with increasing of the solid fraction in filler metal, the bonded ratio of the interface and the tensile strength of the bonded joints increases, until up to the maximum values of 91.2% and 160 MPa respectively when the solid fraction is 60%; afterwards they start to decrease. At that time, a good bond between filler metal and composites appears.