To meet the optimization demands of the piston cooling system in a highly enhanced engine， a CFD model of the piston cooling nozzle jet based on the Dispersed-VOF method was established. The model incorporated the gas volume fraction and was validated by the results of the high-speed camera test under multiple operating conditions. The jet characteristics of the piston cooling nozzle and their influencing mechanisms were systematically investigated. Based on the parameters of jet velocity， turbulence intensity and dissipation， and divergence angle， the influences of engine speed （600~1 800 r/min） and length-diameter ratio of cooling nozzle （1~6） on jet characteristics were analyzed. This study provides the first quantitative revelation of the linear relationship between the gas volume fraction of the jet and engine speed， as well as the linear relationship between the divergence angle and engine speed： for every increase of 300 r/min in engine speed， the gas volume fraction is decreased by an average of 4.2%， and the jet divergence angle is increased by an average of 0.14°. It also finds that the nozzle with a length - diameter ratio of 4 exhibits relatively superior jet divergence characteristics and turbulence intensity during operation， which can effectively improve the oil intake efficiency and enhance the cooling effect.