Water-jet guided laser micromachining is the new development orientation of laser machining. This paper set up the numerical model on the action between the water-jet guided laser and the material. By using the software ANSYS, simulated the processing of the water-jet guided laser micromachining. This paper gave the investigation on the machining laws and the distributing of temperature fielding in processing of water-jet guided laser micromachining. And the results of the correlative experiment prove the model aright. The result provided the theoretical foundation for the next research on the water-jet guided laser machining.