Carbon fiber-reinforced plastics (CFRP) composites are increasingly used in the aerospace and automotive industries due to their excellent properties, which require higher processing accuracy to ensure their performance. Water jet-guided laser processing technology is a modern processing method, which can effectively reduce the thermal damage caused by laser processing. In order to understand the transient thermal effect of water jet-guided laser processing on CFRP materials and its removal mechanism and the influence of the duty cycle of laser pulse on the temperature field distribution of materials, this paper is based on the "element birth and death" technique in the finite element method, the three-dimensional transient temperature field of heterogeneous fiber matrix and the subsequent material removal model are established. The results show that the CFRP composites processed by water jet-guided laser processing can obtain better processing results over traditional laser processing. Adjusting the duty cycle of laser pulses can significantly affects the shape and temperature distribution of the composites after drilling.