To improve the professional quality of elementary and secondary school teachers in Taiwan, the author suggests that educational authorities should carefully plan and implement a differentiated teacher evaluation system. The system comprises three tracks, namely Track I-- The Beginning Teacher Track, Track II--The Professional Development Track, and Track III--The Teacher Assistance Track. To satisfy the different needs of teachers in the different tracks, the evaluation criteria, evaluators, models, tools, procedures, and result treatment should also be differentiated in the system. The planning of the differentiated teacher evaluation system should respect both the voice of evaluation experts and practicing teachers. In addition, the legalization of the system and allowance of flexibility for the implementing institutes are also important. As to the implementation of the system, the author suggests the strategies of incremental change, communication guidance, capable person training, easy implementation, and strengthening the coordinated sets of measures.