This study investigates the alignment between curriculum standards and textbooks, based on a standards-based science education context. The analysis sample includes the High School Biology Curriculum Standards and five editions of biology textbooks in China. Porter's alignment model is used to construct a two-dimensional (content areas and cognitive levels) matrix of curriculum standards and textbooks to calculate alignment indices and marginal discrepancies between the two dimensions. The results show that (1) alignment between curriculum standards and textbooks has not been achieved; (2) textbooks are highly consistent and statistically significant, but independent of curriculum standards; (3) the distribution of curriculum standards and textbooks across various core concepts and cognitive levels is unbalanced; (4) both curriculum standards and textbooks overemphasise the cognitive levels of remembering and understanding, while minimally representing the applying, analysing, evaluating, and creating levels. This study examines the development of curriculum alignment in the context of current worldwide standards-based science education reforms and provides a framework for alignment research based on content analysis.