Aimed at the problem of guide error on machine tool, a mathematical model for space error of double-guide system was established based on the principle of homogeneous coordinate transformation, and the analyzing method was provided. A fixed reference-coordinate system was established on the machine tool body firstly, and the move-coordinate system was separately established on the two machine tool guides. Then the dynamic characteristic of guide errors was analyzed in six degree-of-freedom (6-DOF) move coordinate system. Finally, the comprehensive modeling and analyzing for the space error of double-guide system was carrying out. This comprehensive model can be used to analyze the degree and rule of the error of guide system that influence the tool nose, which provide accurate direction to the error prevention and compensation on whole machine.