Hot extrusion and warm extrusion are the main forming processes of projectile body production,in which more than 10 percentage points of rejects are caused by errors in the dimension,form and position of projectile bodies,which are produced because of the elastic deformation,plastic deformation or deflexion of plunger tip in the forming mould at high temperature and press machine under extrusion force.Therefore,it is of remarkable significance to research and develop an automatic measuring instrument to test the geometric accuracy of projectile body,get rid of the rejects and find out deficiencies inmould or the process in a timely fashion.Based on the construct of a certain automatic warm extrusion production line for projectile body,a novel measuring instrument,combining the contact and non-contact measurement,has been put forward in this paper.With its high precision and long range of CCD laser displacement sensor,errors in the wall thickness,roundness,cylindricity and coaxiality of projectile body can be obtained at one measuring procedure.Besides,the paper has dealt with its working theory,mechanical composition,and soft and hard ware based on open structure CNC system.Also,algorithms of the errors in wall thickness and roundness,together with the compensation method of thermal deformation,have been deduced.Practical use has indicated that this composite measuring system can effectively solve the bottleneck problem of the warm extrusion line for projectile body with high precision and efficiency.