In order to have good tearing performance, the bag body of the outer packaging cocoa powder has a permanent tear opening, and the serrated tear opening is one of them. However, not all serrated tear prone edges have good tear resistance, mainly because the tear resistance of such tear prone edges is closely related to the shape of the cut and the composite strength of the packaging bag. If the shape of the cut is not set reasonably or the composite strength of the packaging bag is relatively low, delamination is likely to occur during the tearing process, which will affect the tear resistance of serrated tear prone edges. Therefore, improving the testing of tear resistance of tear prone edges plays a crucial role in improving the ease of opening of packaging bags.