Linear guides are generally divided into two categories, namely square rails and circular rails. Circular guides were the first to appear, but the accuracy of the square guides was poor. However, the circular guide is ideal for moving heavy loads straight. Which linear guide is used in detail should be determined according to the actual rail application requirements. The various grinding requirements inherent in square rail planning result in several initial cost of round guide rails, but the performance of guide rails with linear guide rails is superior to that of circular guide rails. In general, square rails have higher load capacity, accuracy and stiffness, and longer service life.