Mechanical properties and corresponding microstructures of polyphenylene sulfide(PPS)/glass fiber composites were investigated according to the glass fiber content and testing temperature change. Tensile test results showed that maximum stress and elastic modulus increased markedly with increasing glass fiber content at below the lass transition temperature(T-g) of PPS matrix. Notched Izod impact strength showed a maximum value ar the glass fiber content of 40 wt% regardless of testing temperatures. Scanning electron microscope (SEM) observation of tensile and impact fractured specimens showed that. at the same testing temperature condition, the fracture surface became more rugged as the glass fiber content increased. Polarized optical microscope(POM) observation showed the crack tip bifurcation at the glass fiber surface in tensile fractured specimens. whereas glass fiber breakdown in impact fractured specimens at higher glass fiber content.