A method for measuring geometric error components based on laser tracker is proposed for error compensation of machine tool guideway system. Homogeneous transformation is used to establish the mathematical error model of the guide way system which can comprehensively describe the relationship between the geometric error components and the volumetric errors. Three noncollinear points are selected from the stage of guideway system, and the spatial coordinates of these points are collected by laser tracker. Then the mathematical error model is applied inversely to establish a system of equations including all the geometric error components of guideway system, and finally the error components can be obtained by solving this system of equations. The measuring results achieved by the proposed method are in coincidence with those achieved by traditional nine-line method, and the difference is smaller than 0.74″, which validates the effectiveness of this method. Compared with the traditional methods, the laser-tracker-based geometric error components measuring method for guideway system is easy to implement.