The influence of the rice husks powder (RHP) content and its particle size distribution on the composite’s tensile strength, fracturing elongation ratio, flexural strength and flexural elastic modulus has been investigated. Respective water absorption and thermal properties of PP composites incorporated with different proportion of RHP have also been analyzed. The microstructure of fractured surfaces was further observed in scanning electron microscopy (SEM). The results showed that the composites with RHP of 245 μm have higher mechanical properties. The tensile strength and fracturing elongation ratio decrease with the increase of RHP content, and reach peak values in 30% RHP content. Water absorption and volume expansion ratio of the composite increase with the increasing of RHP content. Flexural strength and flexural modulus decrease after water absorption. When PHR content is low, the RHP particles are well distributed and the interface of RHP and PP is smooth. When PHR content is higher, the RHP particles tend to agglomerate, leading to poorer interface and lower mechanical properties, the composite failed with brittle fracture.