This study used structural topic models (STMs) to analyze physics pre-service teachers' conceptual understanding of scientific literacy. Participants included 126 physics pre-service teachers studying at Shandong Normal University in China. First, we used an open-ended questionnaire to collect the data. Second, STM was used to classify the data, which were divided into nine topics considering information about held-out probability, residuals, exclusivity, and semantic coherence of the words to topics. Third, the focus of these nine topics was explored, and the topics demonstrating gender-differentiated focus were also inspected. Finally, comparisons between the STM results and results of existing studies were performed. The following key findings were obtained: (1) nine topics relating to physics pre-service teachers' conceptual understanding of scientific literacy emerged, such as "beliefs and values about the reliability of information related to socio-scientific issues" and "key ideas of physics in high school." (2) Weak evidence confirmed gender-differentiated attention to only one topic, namely, beliefs and values about the reliability of information related to socio-scientific issues. Further, female pre-service teachers focused more on subjective aspects, while male pre-service teachers focused more on objective aspects. (3) Some of the topics obtained are consistent with the existing scientific literacy frameworks (science content; nature of science; and the relationships between science, technology, and society), while some topics are inconsistent with them; such similarities and discrepancies are discussed in detail, along with the implications of the findings.