For a long time, organizations intend to increase their human resources' efficiency and effectiveness. One of the ways to reach a continous improvement and to an efficiency increase for the employees is the human resources capability which facilitates by providing and developing an influence based on the competence of people and groups on the organization's duties. This article is about to study the effect of personnel OJT on the dimensions of capability.Capability is as a development of competent staff influence in the organization, which its application will be obtained through both formal and informal processes in the organization and be resulted in a permanent improvement in organizational performance through developing qualified and competent teams influence in the most dimensions of the organization which finally affects the total performance of staff and the organization. With regard to the effect of capability in an organization and the importance in the present research, Arak Oil Refinery operational and administrative staff and managers' views on the effect of OJT programs over 5 human resources capability indicators are being studied by data analysis. To complete the results from the distributed questionnaires, the interviewees' views are also reviewed. To access logical results about the effect of In-service traning on the operational and administrative forces capability, findings of the two research tools (questionnaire and interview) mentioned above have been compared with each other. In general, the results show that the OJT is effective on human resources capability indicators (competency/self-efficacy, effectiveness, confidence, self-organization/independence, mean-ingful) as expected.Among the capability components, the confidence and self-organization are evaluated as the maximum and the minimum percentage, respectively. Also, the rate of capability relation with other factors such as gender, place of work and job type was approved in such a manner that the intensity of this relation is more in a type of the employment variable (manegarial / non-manegarial) than that of the place (line up / administrative). In other words, the more training, the more capability, and this influence evaluated more on among administrative personnels than on line up personnels also more on among managers than on non-managers.Accordingly, based on the research findings, it is clear that the personnel OJT has continuously improved the organizational performance, personnel performance, managers' performance and at last the personnel's capability in the Shazand Oil Refinery.