One-dimensional (1D) temperature field model is built to simulate the effects of resin based composites subjected to continuous laser beam. “Phase change enthalpy method” is put forward to deal with the problem of additional heat absorbed during resin decomposition and moving decomposition surface, which simplifies the solving process; then, the model is adjusted using “highest historical temperature pursue method” to revise the model of enthalpy method, which settles the argument between bidirectional change of temperature and irreversible decomposition process. Then, FORTRAN compute program is compiled after discreting the equtions with difference method. Results from calculation and references agree well. Using the model, the relationship between laser parameters and composites temperature is studed at last.