The invention discloses an assistant decision system for condition-based maintenance and risk evaluation of power transmission and transformation equipment, which is composed of six navigation buttons and functions thereof wherein the six navigation buttons comprise a condition-based maintenance button, a task processing button, an inquiry statistics button, a data maintenance button, a system management button and system help button, and the system is additionally equipped with five shortcut menus such as a condition parameter early-warning menu, an equipment state early-warning menu, an equipment indexes menu, a user information menu and a system logging out menu. The invention provides a whole set of the assistant decision system for the condition-based maintenance and the risk evaluation of the power transmission and transformation equipment which has simple operation, detailed content, complete functions, convenient and fast execution, high efficiency and friendly man-machine interaction interface.