根據研究結果，本研究針對實務應用及未來研究提出相關具體之建議與作法，提供政府機關、單位主管以及後續研究者參考，以作為提高工作績效的依據。 This study is to be for the purpose of discussing the problems caused by the fact that the current government employees’ efficiency evaluation system hasn’t been able to fully reflect the real job performance. In that case, the performance appraisal unspoken rules have emerged among the government employees’ efficiency evaluation system. Performance appraisal unspoken rules also have an impact on their organization commitment and job performance. The research mainly talks about the Impact of performance appraisal unspoken rules on organizational commitment and job performance. This research took the questionnaire-survey approach to collect totally 179 valid data. The subjects are the government officials. The survey consists of four parts: variants of unspoken rules of performance appraisal system scale, organizational commitment scale , job performance scale and basic personal data scale. Using the techniques such as researching previous studies and surveying, then analyzing the results through LISREL software. The findings are as follows: 1. Performance appraisal unspoken rules is positively related to job performance; 2. Organizational commitment has partial mediating effect on the relationship between Performance Appraisal Unspoken Rules and Job Performance. Constructive advices would be offered in the research as the reference for the government to amend future performance appraisal system.