Focusing on the quantitative research on feed system with installation errors, a theoretical analyses model is developed to analyze the influence of parallelism error and coaxiality error of the system. The change law of stress, deformation and contact angle is discussed based on the analysis with hertz contact theory. The theoretical analysis is verified by the simulation with FEM software. The result shows that bias load, deformation of guide and compress variation of the ball decrease as the deviation from bearing for the coaxiality error, while these changes remain small for the first half stroke and dramatically increase later for the parallelism error. The analysis above may be helpful for the installing of the ball screw and for improving the machining accuracy.