In order to make the structure of shotcrete robot's arm more reasonable,the modal analysis on the structure of shotcrete robot's arm was carried out by finite element method,and the vibration modes from the first to the tenth order of the arm system were obtained.Based on analysis of the vibration modes,some modification opinions were put forward to optimize the structure of shotcrete robot's arm.The practice proved that the results of modal analysis provided a theoretical foundation for the structure design of shotcrete robot's arm,it can effectively shorten the development time of shotcrete robot and improve the design quality of shotcrete robot.