Based on the stiffness matrix of the modified Delta mechanism that is defined as the Hessian matrix of a potential, a stiffness mapping model of the mechanism, which reckons the influence of the change of the mechanisms configuration and all parts elastic deformation under the constraint force, was established. By using the model, the elastic deformation of the mechanism under different positions and different external loads could be obtained. At the same time, a flexible bar could be produced by integrated the ADAMS/flex module of the ADAMS software. Some original rigid bars could be replaced by these flexible bars; so, a rigid flexible hybrid virtual prototype of modified delta parallel mechanism was established. By virtual component, the drive and the motion pairs of the various bars were added to implement. At last, elastic deformation of the model is simulated in ADAMS software under different moving position and external load, so, theoretical calculation and simulation are verified mutually correct.