A slide guide is the core component of a machine tool feed system, and its wear significantly affects feeding accuracy, machining accuracy, and product quality. This study aims to obtain a suitable wear calculation model for the slide guide under working conditions. The slide guide is a typical plane sliding pair. Based on the principle of friction fatigue, the wear model of plane sliding pairs had been previously established without considering lubrication. Actually, the friction surface of the slide guide is in the state of boundary lubrication when it works normally. In this study, the analysis on the interactions among friction surface asperities covered with a boundary film indicated that the wear model of plane sliding pairs was also applicable to calculate the wear of the slide guide under boundary lubrication by substituting the friction coefficient µ and the fatigue exponent k under lubricating conditions into the wear model. Then, a series of pin-on-disc wear tests with material specimens of the slide guide under boundary lubrication were designed with the working load and working speed of the pair as the experimental parameters. The comparison between the experimental results and calculated results showed that the wear model of plane sliding pairs could be used to predict the wear of the slide guide under boundary lubrication. The wear model reflected the quantitative relationship between the wear rate of the slide guide and its main influencing factors. The study also provides the basis for the tribological design and precision design of the slide guide.