The manufacturing process of helical blades, the core tillage parts for boat-type 1GMC–70 stubble burying rotary tiller, was analyzed and the process errors and their influence on tillage performance were investigated. Results showed that the approximation process used resulted in space straight lines on different planes formed by rotating axis of the helical blade and the blade roller, between which the vertical distance is 204.2 mm and space angle 28.7°. The rotary radii of points on helical blade leading edge, the static sliding cutting angles of helical blade and the static cutting angles of helical blade are ranging from 189.0 mm to 200.0 mm, 14.7° to 32.4°, 70.3° to 73.7°, respectively. Static sliding cutting angle on the end of the helical blade is the smallest, which is 14.7° and belongs to cutting mode, resulting in stubble winding on the end of the blade during tillage. Rotary radius and static cutting angle on the end of helical blade are both the largest, which are 200.0 mm and 73.7° respectively. These factors influence the tillage depth of the tiller in a single performance.