Abstract: In ultraviolet induced nanoparticle colloid jet machining, the nanoparticle colloid microjet is used to effectively remove the material of the workpiece surface. A computational fluid dynamic model for vertical non-submerged jet is established to investigate the impacting hydrodynamics in ultraviolet induced nanoparticle colloid jet machining using a micro hole light-liquid coupling nozzle with an outlet diameter of 500m. With this model, the energy characteristics of fluid field and pressure distributions in the process of ultraviolet induced nanoparticle colloid jet machining are computed under the condition of vertical injection. Through numerical investigation, the dynamic response of two-dimensional TiO2 nanoparticle colloid jet impacting on a plane surface is studied. The simulation results indicate that the injection velocity of the TiO2 colloid in the micro-liquid coupling nozzle is about 30m/s when the jet pressure is 1 MPa, and the uniform bundling jet distance is about 5 mm. The static pressure of the nanoparticle colloid jet in the core area is concentrated, therefore the dynamic pressure and the velocity distribution of the synthetic velocity in the area of the impact of the colloid impinging jet is W shaped, and the maximum value is at the 2 mm diameter of the colloid jet.