Friction is a characteristic that can be found in machine elements in common engineering use, and it has great effect on the machining performance of a machine tool. Linear motion (LM) guides supported by rolling elements are used for accurate positioning of precision machine. For accurate positioning, the frictional behavior of the LM guide must be understood. In this investigation, a new experiment is conducted to measure friction, and the behavior of LM roller guide friction is measured under various external loads, preloads, velocities, and lubricants. The results obtained from experiment are compared with reference data, and the experimental friction equation of LM roller guide THK SRG25 is achieved from experiment, which can be used to calculate LM roller guide friction and control positioning accuracy.