In view of the lack of comprehensive consideration of equipment condition-based maintenance and grid operation in the optimization of decision-making， an optimization model for condition-based maintenance decision-making for transmission equipment is proposed that takes into account both the equipment failure risk and grid operation risk. With“minimum integrated risk cost” as the optimization objective and such restrictions as simultaneous maintenance， exclusive maintenance， repair resources， network security， etc as constraints， the solution for the model should be found using the Tabu search algorithm while considering the changes of the equipment failure possibility before and after the condition-based maintenance. Risk comprehensive evaluation is achieved by risk economic quantification to obtain the best technical and economic maintenance program. The effectiveness of the optimization method is illustrated with an example in the power grid of a certain area in East China.