Aimed at the high cost of linear measurement for CNC machining center by using laser tracker, a threedimensional laser interference double-ball-bar was developed. The laser interference method was used to measure the distance, a new measuring optical path was designed, and the following measurement was realized by the passive stretching of the extension rod. The double spherical joint motion pair was used to ensure the space attitude adjustment of the laser, and the laser, mirror group fine adjustment and other devices were used to realize beamfocusing at any time. ANSYS Workbench software was used to model the device and verify the model accuracy. The kinematic equation of the mechanism was established, and the motion space was simulated by using MATLAB. The laser path was verified by experiments, and the feasibility of the design was proved.