For the reliability problem of valve clearance adjusting sheet of a vehicle diesel engine, the fault tree analysis was carried out to analyze the failure mechanism of adjusting sheet, the reliability model based on the engine durability test section was established, and the existing reliability of adjusting sheet was evaluated. The reliability growth measures of adjusting sheet were analyzed from the aspects of structure, materials and process, the reliability growth effect was further evaluated based on the reliability model and the verification test was finally conducted. The research shows that the failure mode of valve clearance adjusting sheet is contact fatigue failure. By adopting the reliability growth measures such as optimizing the structure and process parameters and replacing materials, the reliability of valve clearance adjusting sheet improves significantly.