In recent years, with the BIM technology application matures in the field of construction engineering in our country，BIM is becoming more and more widely applied in the field of building water supply and drainage design, the effects of it is becoming more and more profound. In view of this, in this paper, the application of BIM technology in building water supply and drainage engineering design, as well as the present problems of the BIM are analyzed.

By using the technology of CAD drawing and standard design calculation is very necessary and feasible. Designers can use the technology of parametric drawing, carries on two times of CAD development of the use of VBA language, the water processing graphics processing and engineering graphics rendering and completed in the computer, realize the parametric design of water treatment structures. Users only need to input the basic parameters that can be completed treatment structure graphics and rendering in CAD, reduce the processing procedure and time complexity. Based on the traditional plug flow aeration tank as an example, introduces the parametric design of traditional plug flow aeration tank by VBA.