Coagulation mixing is an important process in water treatment technology, the research of coagulation mixing has engineering practice reference value. Through a series of coagulation jar test, the effects of changing the shape of containers and the geometric size on the settling efficiency of flocs and final turbidity removal rates were researched. The experimental results show that the hydraulic conditions of the square container were more favorable for the growth of the flocs, and the coagulation effect is better than the circular container.