Aircraft cockpit display system has developed from traditional 2D to multi-dimensional display mode. As a human-computer interface development tool VAPS XT can improve the design efficiency of cockpit display but does not support 3D display design directly. We proposed a scheme for second development of VAPS XT which supports basic 3D cockpit display simulation design with default VAPS XT configuration by use of OpenGL library and DEM elevation database thus to realize 3D cockpit display development with VAPS XT. This paper introduces the development process of 3D cockpit display with VAPS XT including the user development process data processing of 3D terrain database coordination transformation and foundation of rendering process. The whole process can be applied as new way for cockpit human-machine interface development. The simulation result shows that the process is an effective and convenient verification technology for 3D cockpit display design and simulation.