This study applied three-phase flow simulation to simulate the effect of four different types of overflow pipes on clarification. These four types of overflow pipes include: a 9 mm straight pipe (9-9), divergent overflow pipe (9-12), convergent overflow pipe (12-9), and a 12 mm straight pipe (12-12). The results indicate that under similar split ratios and other variables of similar operations, the converge type overflow pipe can obtain much more supernatant liquid, with greatly improved separation efficiency.