This paper is about the process of developing integrated science curricula at junior secondary schools in the Peoples' Republic of China in the past 20 years. The history has witnessed two stages of developing integrated science curricula during this period in China: one was at the provincial level in the 1980s/1990s, while the other was at the national level in the new millennium. Using the concept of curriculum emphases, this paper purported to investigate the advocated forms of integration and the reasons and causes behind them in integrated science curriculum during the period under study. Data were collected from two sources: curriculum documents related to the integrated science curricula, and interviews with key informants who were involved in designing the official documents of this kind of science curriculum. Two models of integration have been identified from the two stages respectively: one is "integration within science subjects", while the other "integration beyond science subjects". The social-political roots of the two models of integration have been traced. To meet the goal of scientific literacy, it is suggested in the final part of this paper that the model of "integration within science subjects" should be abandoned while the model of "integration beyond science subjects" should be advocated in the process of developing integrated science curriculum. (Contains 1 table and 3 notes.)