The equal-cycle preventive maintenance strategy is widely used due to its simplicity and ease of implementation. However, existing optimization models typically adopt a coarse modeling granularity and rarely account for fault differences, particularly the varying effects of preventive maintenance on different failure types. To address these limitations, this study takes the meta-action unit as the basic research object and classifies unit failures into damage failures and intrinsic fatigue failures, while explicitly considering the differing impacts of preventive maintenance on these two failure types. A hybrid failure-rate model is used to characterize imperfect maintenance effects, and an optimization model for an equal-cycle imperfect preventive maintenance strategy is developed. Numerical analyses are performed to verify the effectiveness of the proposed model and to investigate the influence of different maintenance cost structures on the optimal maintenance cost rate and maintenance strategy. The results indicate that neglecting differences in preventive maintenance effects leads to an underestimation of the maintenance cost rate of the meta-action unit, and that both maintenance cost types and the proportion of failure modes have a significant impact on the determination of the optimal maintenance strategy.