This study aims to understand the STS ingredient in three versions of fifth-and-sixth-grade textbooks in Taiwan. Topics with similar theme and with significant different STS ingredient among different versions are selected for comparison. The information can provide insight for textbook writing or improvements in teaching. Three in-service teachers use STS Teaching Evaluation Indicators as instrument for content analysis. Scorer reliability among these evaluators is 0.96. After the evaluation, topics for further comparison are selected and contents are then analyzed. The research findings include, 1.Themes related to environment and everyday living are more easily integrated with the STS instructional approach. 2.To a similar theme, different versions adopt different approaches. Approaches beneficial to STS are identified. 3.The adoption of (1) societal issues, (2) information collection and problem solving, (3) respecting for oneself and different viewpoints, and (4) anchoring learning with real life situation, will substantially enhance the STS ingredients of science textbooks.