Recycled plastic with different particle size and impurity content were compounded with cotton stalk particles,after which the mixture was used to make cotton stalk/plastic composites through hot pressing.The effects of size and impurity of the recycled plastic on the composite properties were evaluated.The results show that: 1) the physical and mechanical properties of composites made with smaller plastic sizes perform better than those made with larger plastic sizes;2) cleaning the recycled plastic with water is more effective for improving the composite properties than increasing the waste plastic content.