The "Investigation of Longhuai Mud Drainage Reservoir of Guangxi Huayin Aluminum Co., Ltd." completed in 2015 won the second prize of Excellent Engineering Investigation Achievements of China Nonferrous Metals Construction Association in 2019. The newly-built Longhuai mud discharge reservoir belongs to the third-class reservoir, with five outer dams and one inner dam. Through various geophysical prospecting and drilling verification, combined with the understanding of karst development law in karst investigation, this project comprehensively finds out the karst characteristics of the site. Longhuai mud discharge reservoir runs safely and well.