Abstract: There were many problems after 2.5 dimensional carbon fiber reinforced SiC ceramic matrix (C/SiC) composite processed by nanosecond lasers, such as ablative oxide layer, sidewall slope, uneven bottom surface, and many problems also remained in grinding processing, breakage of fiber and matrix, fiber fracture, tool wear, low shape accuracy, low efficiency and so on, the laser-grinding compound processing method was proposed. To explore the feasibility of laser-grinding compound processing of 2.5 dimensional C/SiC composite grooves, the grooves experiment of laser processing, grinding processing and laser-grinding composite processing were carried out. The results show that the slope of the side wall of the groove by laser processing is about 23°, the surface quality of the bottom and side wall is poor, but the processing efficiency is high. To a certain extent, the surface quality of the grooves by grinding is improved, but the shape precision of the grooves after grinding is extremely poor and the processing efficiency is lower because of the severe wear of the grinding wheel. However, after laser-grinding compound processing, slope of groove sidewall is removed, the grinding wheel wear is greatly reduced, and the surface quality is significantly improved, roughness of the groove surface is 1.27-1.96 times higher than that after grinding, the processing time is about 0.3 of that of grinding. Therefore, the laser-grinding compound processing can not only overcome the shortcomings of laser processing and grinding processing, but also give play to the characteristics of high laser processing efficiency and grinding accuracy, and take into account the quality and efficiency of groove processing of 2.5 dimensional C/SiC composites. The results can provide theoretical support for efficient, precise and low damage processing of 2.5 dimensional C/SiC composite grooves.