<p>The effective articulation of the nature of science (NOS) in cross-level textbooks is a basic requirement for the science curriculum. This study examines this issue using biology textbooks in mainland China. Guided by the family resemblance approach extended version framework, it analyses the articulation of NOS in elementary, middle, and high school biology textbooks in mainland China and derives four results. First, the comprehensiveness of NOS categories in high school biology textbooks is greater than that in middle and elementary schools; however, this advantage is only reflected in the compulsory modules of high school biology textbooks and is weak in the optional modules. Second, the frequency of social-institutional systems is low in elementary and middle school textbooks; this deficiency has not been properly addressed in high school textbooks. Third, the ‘economics of science’ and ‘social certification and dissemination’ categories are consistently neglected at all three textbook levels. Fourth, a high degree of repetition is observed in the processes of selecting NOS-embedded cases and describing content in some of the categories in both middle and high school textbooks. These results highlight an urgent need for textbook revision.</p>