Abstract: For an accurate prediction of the friction experienced by the linear rolling guide and the factors affecting it, the fluid lubrication state of the rail was considered, and the effect of the friction of the linear guide on the ball contact angle and preload was studied based on the Hertz contact theory. Based on the Hertz contact theory, the static equations and the ball-raceway contact mechanics equations of the linear rolling guide were established for vertical loading. Using the Hertz contact theory, changes in the ball contact force of the linear rolling guide were analyzed. Combining the analysis of the critical load and the oil film obstruction between the balls and the rail, a friction model was established for studying the effect of the external load. Experiments were carried out on a domestic model of the linear rolling guide to validate the developed friction model. Through the analysis and comparison of the experimental and theoretical data, the influence of the resistance of the lubricating oil film, the contact angle, and the preload on the friction of the linear guide were verified. The results show that the friction of the linear rolling guide, under the condition of lubrication, is affected by the contact angle and the preload force.