The current research on the maintenance strategy of agricultural equipment is mainly based on equipment failure data and degradation, which often cannot guarantee the task success of the equipment in a specific operation process, thus making it difficult to meet the requirements of modern agriculture for high task completion of agricultural equipment. To address this problem, a task-based maintenance strategy for agricultural machinery and equipment was proposed. Firstly, based on the correlation between the degradation state of each system of agricultural equipment and the task reliability of the equipment, an assessment model of the task reliability of agricultural equipment was established. Secondly, using the Monte Carlo method, a comprehensive assessment process of the task reliability of agricultural equipment was given, and the task reliability of agricultural equipment under multiple operational tasks was described quantitatively. Then, based on the correlation between the task reliability of agricultural equipment and the maintenance cost, an algorithmic model of the optimal maintenance inequality cycle and optimal maintenance times for each system, which met the constraints of minimum reliability and minimum maintenance cost, was established. Finally, an opportunity maintenance strategy was adopted to establish a maintenance optimization model for agricultural equipment. Taking the historical fault data and maintenance cost data of domestic wheel tractors as examples, the optimal maintenance schedule arrangement based on the optimal opportunity maintenance threshold was obtained. When the optimal maintenance threshold was 8h, the maintenance cost was 2.587 yuan. Compared with the traditional maintenance strategy of agricultural machinery equipment, the total maintenance cost was reduced by 30.4%. The proposed method was helpful to improve the task completion rate of agricultural machinery equipment, reduce the failure rate and maintenance loss of agricultural machinery equipment.