Abstract: Aiming at solving the problem that it was difficult to prepare cross-sectional transmission electron microscope (TEM) specimens for brittle materials, an improved ion milling method for preparing TEM specimens was detailed described. First preparing stacked rectangular sheet, secondly cutting stacked rectangular sheet with low speed diamond wheel saw to get thin stacked sheet, thirdly cutting out the wafer of 3 mm, and finally grinding, dimpling, polishing and ion milling to complete the specimens preparation. According to a large number of preparing test, it was confirmed that this method had advantage of low cost, being easy to operate and improving the preparation success rate. By using this method it could quickly succeed in preparing thin film samples grown on Si substrate, and clearly observed the growth situation of the film layers in TEM.