A number of researches and on-site evaluation reports on comprehensive high school (CHS) have been made since the Taiwanese government launched the policy of CHS. However, most of their findings were not tenable due to the imperfect and incomprehensive data and the aim of on-site evaluation was mainly to find the problems of implementation. Since the model of ”Program Theory Evaluation (PTE)”, a new approach of policy evaluation, was used to analyze the policy of CHS in Taiwan. The aims of this research were to: (1) probe into the change theory of policy of CHS in Taiwan; (2) evaluate the feasibility of change theory which the CHS policy is based on; (3) explore the policy implementation of the 'CHS policy, (4) make some suggestions. Document analysis, in-depth interview, focus group interview, and questionnaire survey were used, and some important findings were concluded.