Abstract: This article briefly shows the structure of the FZ-12 solid-liquid separator and its technological process in treating sewage. By experimenting with solid-liquid separator in the treatment of sewage before it is discharged on three large scale pig farms, we come to the conclusion that solid-liquid separator is effective in gathering dung sullage, with about 2.9 t/h and the water content less than 55%. The average rates of removal of TS, COD, and BOD are 82.5%, 77.5% and 73.5%, respectively. By investing 53 thousand yuan on the solid-liquid separator and making it work, the pig farm can earn a profit of 45 thousand yuan annually, with the return rate of 84.9% and the capital return period of 1.18 year. Therefore, FZ-12 solid-liquid separator has a very bright prospect in treating pig farm sewage.