Abstract: To calculate the deformation of a rolling linear guide in all directions under any external load, a model of contact stiffness of roller linear guides was set up by the homogeneous transformation matrix. The model calculated the elastic deformations of different balls by the presence of under any external load considering the changing preload and contact angle. The elastic deformations along two axes and three deflection angles around three axes were calculated. Furthermore, the linear stiffness of two directions and the torsional stiffness of three directions were obtained. The stiffness models were analyzed and compared with the actual situation. The simulation analysis prove that these mathematics models are right. The influence laws under the changing preload and the contact angle of the rolling linear guide to its stiffness are found.