The structure of spray gun is one of the most important parts of dry ice cleaning system, its performance will directly determine the performance of the system. By comparing the characteristics of straight type and Venturi type spray gun, the Venturi spray gun is chosen as the prototype. Through the combination of theory with Fluent discrete phase simulation, the gun Venturi was analyzed to obtain the effects to airflow and particle phase when geometric parameters changed, and by changing the guns parameter: length of channel contraction, contraction angle, throat diameter and throat length, angle and length of extended segment and the coupling effect to optimize the spray gun. Finally, the geometric structure of the spray gun is designed which is suitable for high and cold, high pollution, high live working safety requirements of catenary rod insulator and can meet the cleaning requirements of middle and long distance in high voltage electric field, and it provides a reference for the future of dry ice cleaning for catenary insulator.