This paper studies the applicat io of CA D technolo gy in g un overall desig n. The funct io n requirement s of gun o ver al l design CAD system are analy zed on the basis of co nsidering the characterist ics of gun design and the needs of users. An integrated system st ructure in mult iple-grade tr ee shape has been presented. T his system has been developed on SGI w ork stat ion. T he integ rated sy stem is centered o n at ive three-stag e database, w ith interact ive g raphic system being method and its main body of engineering analysis and calculagion. T his system is of signif icance in both theory and appl icatio n as to impro ving the gun deingn quality, reducing r esearch cycle, and decreaing the co st .