Abstract: The processing capacity of the economical CNC lathe is limited by the number of original tool positions. Although the processing capacity is expanded by adding tool positions on the skateboard, the eccentric error of the drilling, expansion and reaming tool installation is large due to the modification and tool adjustment errors. It is not suitable to drill, expand and ream deep holes directly on the lathe, and it is more difficult to adjust the tool position. Therefore, it is necessary to study the modification process of the tool position to reduce the difficulty of adjusting the tool position while improving the accuracy. Through the analysis of the processing characteristics of the lathe hole, the targeted row tool holder structure is designed, and the manufacturing process of the modified row tool holder is formulated according to the structural characteristics and accuracy of the lathe itself.The research results show that the designed tool holder structure is suitable for increasing the number of tool positions on the lathe. The position accuracy obtained by the modification process depends on the accuracy of the machine tool. It is not necessary to adjust the tool on the x-axis and y-axis when changing the tool to achieve rapid tool change. Eliminate the tool adjustment error, improve production efficiency, and maximize the accuracy of hole processing.