One dimension model of the coaxial explosive magnetic generator (CEMG) has built up. The model consists of 1-D model for explosion driven central tube(armature), 1-D model for magnetic flux diffusion, 1-D model for conductor resistivity and the circuit model. A code (CEMG 2.0) was compiled. With the aid of code CEMG2.0, the 43 cm Ranchero generator designed by LANL has been calculated. The results agrees well with the experiments and the calculation of code RAVEN provided by LANL.