Shell gasifier 17 primary water treatment unit mainly includes 3 aspects namely the separation of acid gas from waste water, the separation of solid ash in waster water and the recycling of the clarified water. The processing procedure and characteristics of the 3 parts water treatment process were introduced. It is pointed out that the 17 primary water treatment unit fully embodies the concept of energy saving and environmental protection, the separation of useful substances in waste water and the use of the clarified water after waste water treatment have been solved.