This paper aimed to explore the factors that influenced teachers’ adaptations of the curriculum materials of the new senior secondary chemistry curriculum, a standards-based science curriculum, in China. This study was based on the premise that the interaction of the teacher with curriculum materials in a given social context determined what happens in classroom. An interpretive approach was employed and six chemistry teachers in four senior secondary schools participated in this study. Classroom observation and interview were used as research methods. The data analysis revealed that there were seven factors that led to the teachers’ adaptations of curriculum materials, and these factors were teacher’s pedagogical content knowledge (PCK), external examinations, time constraint, teaching resources, class size, belief about science, and peer coaching. Among these factors, teacher’s PCK, external examinations, and time constraint were the more significant factors that influenced teachers’ adaptations of curriculum materials. These factors were discussed in the social contexts of China in the last section of this paper.