The purpose of this study was to develop teacher's self-assessment scale and to propose the procedure for improving the quality of teaching activity. The reason for self-assessment for teachers is to encourage and sustain professional growth. As professional educators, teachers are constantly evaluating themselves as they interact with peers and students. It is useful and necessary as well to practice periodically in a more formal process and procedure that gives teachers opportunity to reflect on recognized excellence in teaching activity. In this point of view, if it is allowed to activate in positive school environment, self-assessment as a part of teacher evaluation can be the most powerful force available to teachers to improve teaching behavior, strategy, technique and to support an internal drive in all teachers to constantly improve their teaching professionalism. Although the self-assessment scale and procedure in this study wasn't be verified the feasibility in school, it will can be helpful to beginning teachers and experienced teachers those who have need to develop and improve their teaching performance competence