The purpose of vacuuming the slurry beyond hydrolysis. The slurry is delivered to the press cloth of the vacuum belt dewaterer via a heavy rubber belt with longitudinal grooves and a through hole in the middle so that the liquid needs to be discharged from the empty tank. Filtrate and air are pumped to the vacuum main pipe at the same time. The filtrate in the vacuum filtrate collection tube is transferred to the gas-liquid separator to expand the gas-water separation, and the top outlet of the gas-liquid separator is connected with the vacuum pump, and the vacuum pump is exhausted. The filtrate after separation is transferred from the bottom outlet of the gas-liquid separator to the filtrate to take over the water tank. After vacuum suction, the slurry passes through the forming area, washing area and wet area to form qualified filter cake, which is then sent to the unloading trough in the unloading area and sent to the gypsum warehouse by the conveyor belt. Vacuum belt dehydrator is also called the same vacuum chamber type rubber belt filter; On the basis of introducing, digesting and absorbing similar products from abroad, it develops a new, efficient and reciprocal mechanical equipment for separating solid and liquid from operator. At the same time, it is also a mechanical equipment for building solid and liquid separation by making full use of material gravity and vacuum suction. In the structure, the vacuum zone is arranged along the horizontal direction, and the length of the vacuum zone can be used to count down the different process of filter, washing and drying, etc. It has the advantages of high filter effect, large production capacity, good cleaning effect, wide application range, simple operator, stable operation and convenient maintenance, etc. Especially suitable for filter solid phase particle coarse, high density and filter cake must be repeatedly washed suspension slurry, can be widely used in metallurgy, mining, chemical industry, paper making, food, pharmaceutical and environmental protection and other industrial sectors of solid liquid separation; Especially, gypsum hydrolyze in flue gas by-product (FGD) of wet process has good application.