Although the content of science lessons has been analyzed from different perspectives by developing a set of codes (e.g., K. J. Roth, S. L. Druker, H. E. Garnier, M. Lemmens, C. Chen, T. Kawanaka, and R. Gallimore, (2006), Teaching science in five countries: results from the TIMSS 1999 video study, Washington, DC: National Center for Education Statistics), none of the existing coding systems have investigated it from a subject-specific and dynamic perspective. Aiming to fill this gap, this study develops a content coding map (CCM) to classify the content of chemistry lessons (CCL) into 12 types based on their roles and values. The CCM was constructed based on semi-structured interviews and revised by applying the initial CCM to six videotaped lessons. Furthermore, the coding was reviewed by an expert committee to confirm the content validity and evaluated by 86 in-service teachers using a questionnaire with responses measured on a five-point Likert scale to test for face validity. These 12 types of CCL were organized into five related groups in the CCM: core knowledge and practices (CKP), connections among CKP (C-CKP), expansion of CKP (E-CKP), scaffolding for CKP (S-CKP), and meaningless content in relation to CKP (MC-CKP). Each group is illustrated and discussed using specific types of CCL. The CCM, which provides a new way to explore chemistry classrooms, can be used as an analytic tool for chemistry educators to investigate the CCL and can serve as a guide for chemistry teachers when designing lessons.