A special NC machine was designed which could be used to process 8 holes in 4 groups at a time in view of the disadvantages of the general machine, such as the large size of the boom of the loader, the high processing precision of every group of the holes system, the difficult clamping of normal boring machine and floating boring machine. The general structure of the machine, the working principle and the technical parameters were introduced. The design of the boring head of the machine, the spindle box and the fixture system were discussed as well as the complex boring arbor. The distance of the main spindle of the machine can be adjusted automatically, it meets the demand of the changing holes distance of many different kinds of the boom. Such a machine is efficient in processing boring holes of boom.