Abstract: To achieve the purpose of fine preventive maintenance operation, a preventive maintenance timing decision model based on repairing degree and performance deterioration was proposed for timing judgment of preventive maintenance of asphalt pavement. Considering the short-term and long-term effects of preventive maintenance, the concept of repairing degree was proposed. Cost-benefit and environmental benefit analysis methods were used to determine the optimal time of maintenance from two dimensions: maintenance repairing degree and performance deterioration. By verifying the model, it is concluded that the best time for preventive maintenance is when the pavement performance index (PPI) value is 90 and the repairing degree is 60%. When the PPI value is 85.0-87.5 and the repairing degree is 80%-95%, greater environmental protection effect can be obtained. Results show that preventive maintenance under the standard of relatively early maintenance time and relatively high road condition level can obtain greater economic and environmental benefits. The proposed method provides research foundation for highway maintenance agencies to conduct project selection, especially in the case of limited funding and environmental protection, and it can also be used for the fine-tuning maintenance.