Aiming at the problem of insufficient consideration of accessibility of spare parts in the maintenance decision model of k /N (G) system under the traditional m condition-based maintenance strategy, the (m,Q) maintenance strategy and the joint decision-making optimization method of spare parts ordering and production are proposed, and the joint optimization model of spare parts supply and demand for k /N (G) system under two condition-based maintenance is established. It is proved that the joint model under (m,Q ) condition-based maintenance strategy, we call this model the (m,Q,n) strategy model, has the order threshold m, order quantity Q and order number n with the minimum objective function while satisfying the constraints, and the joint model under m condition-based maintenance strategy, we refer to this model the (m,n) strategy model, proves that the objective function has the minimum value at optimum order quantity m and optimum order number n while satisfying the constraints. In addition, the effects of different model parameters on the decision-making of the two models are compared and analyzed, the results show that the cost of the (m,Q,n) strategy model is always less than that of the (m,n) strategy model and the operational availability of system is always higher than that of the (m,n) strategy model.