Abstract: The shock wave optimization was carried out for the turbine variable nozzle of a turbocharger under the conditions of large expansion ratio and small opening. Firstly,the Hicks-Henne type function that can consider the global and local characteristics was innovatively introduced to parametrically design the nozzle blade shape. Then,a weighting method of maximum circumferential gradients of static pressure was proposed to quantify the intensity of nozzle shock wave. Finally,the multi-objective optimization of the nozzle blade shape was implemented based on the radial basis function and NSGA-Ⅱ genetic algorithm. The results show that the equivalent strength of the nozzle shock wave is reduced by 68.88%,the total pressure loss is decreased by 25.77%,the turbine adiabatic efficiency is increased by 3.57%,and the change of mass flow rate is not more than 4%. The optimization has greatly weakened the shock intensity of variable nozzle without reducing the turbine aerodynamic performances.