Polymerization of plastic ball translucent crystalline polypropylene composite plastic ball of environmental protection and safety, the proportion of plastic PP ball is 0.89-0.92g/cm3, lower than the proportion of water, all plastic raw materials is the lightest plastic ball, good stability of plastic PP ball in the water, not water, put into the water shrinkage test of PP plastic ball. From the numerical point of view, basically negligible, the total molecular plastic was between 7.9 149 thousand PP ball case, small plastic injection molding easier than PP PP ball, plastic ball injection molding difficulty 15mm increase, mainly for the size of plastic ball PP shrink seriously. It is difficult to ensure the needs of the plastic ball diameter is the main method to improve. Plastic mold PP ball with cooling water, so that the molded plastic PP ball rapid cooling, so as to ensure the size and accuracy of plastic PP ball.