Water-jet assisted nanosecond laser process was used to avoid the process defects of traditional nanosecond laser on wood. Korean pine was used as the experimental material. A factorial design of experiment was performed. The influence of cutting speed and laser power on the kerf width was compared with and without the water-jet assisted system. The surface morphology of processed wood kerf was observed via scanning electron microscopy (SEM). The results showed that kerf width increased with increased laser power and decreased with increased cutting speed. When the cutting speed was 50 mm/s and the laser power was 6 W, the minimum value of the kerf width was 0.26 mm with the water-jet assisted system involved, and the surface quality was excellent. The experimental results were processed by analysis of variance and multi-linear regression analysis. Moreover, prediction model of process parameters and kerf width was established, and the prediction model had better prediction accuracy, providing certain theoretical basis for predicting kerf width of wood processed by water-jet assisted nanosecond laser.