errors, a model is developed to analyze load distribution of ball screw with errors in various load conditions are theoretically investigated. Negative errors makes the load on ball or guiding grooves in corresponding position smaller, even there is no contact in the position when the negative errors reaches certain value. Positive error makes the load bigger. If error heights are assumed to be normally distribution random, the load distribution without error is average value of that in random-error contact. It is valuable for equilibrating load distribution to correct nut groove. The simulation results show that model proposed in this paper is significant to study characteristics of ball screw with regard of errors.