This cross-sectional study examined materials adaptation within an English-Chinese bilingual storytelling curriculum for first graders to identify the potential factors influencing adaptation choice. It delved into the relationship between curriculum objectives, perceptions of picture books, and the use of tense and narrative. A survey (N=352) gathered demographic data of English teachers from China, and the data was analyzed using Partial Least Square (PLS) structural equation modeling. Findings illuminate how teachers' perception of picture books fully mediate the interplay between bilingual storytelling curriculum objectives and teachers' narrative in a picture book adaptation. Analyzing the results by narrative theory, it found that the essence of storytelling and narrative is making meanings; stories play a leading role in the curriculum for first graders to develop their bilingual narrative through sharing, reading, and telling stories. Consequently, teachers' understanding of picture books' possibilities as teaching materials, benefits for fostering students' bilingual development, and perception of the intertextuality of illustration and words can significantly facilitate teachers' narrative in a picture book adaptation. This study contributes by elucidating the mediating role of picture books, emphasizing the importance of linking curriculum objectives with teaching materials adaptation in practice. Furthermore, longitudinal research is to overcome the limitations of this cross-sectional correlation analysis.