This study is the subproject of “the enactment of curriculum guidelines of 12-year basic education and capacity-building at schools” integrated project, examining the curriculum transform and praxis of comprehensive high schools and teachers. This study adopts the design-based research, selecting one of each urban/rural schools as case study subjects and takes two years and five months to conduct two stages of research. The first stage is about comparing urban/rural comprehensive high schools teachers’ understanding and praxis of curriculum guidelines of 12-year basic education and the difficulties it faces. The second stage is about researchers and the case study participant school cooperating together to examine capacity-building programs in curriculum transform and implement guidelines. It aims to build a proper mode in response to comprehensive high schools implementing curriculum guidelines of 12-year basic education. The author proposes national level of guidelines development and school level of curriculum transform for the future.