The present study aimed to explore learning performance and gains in two different tutoring styles, i.e., directive tutoring and facilitative tutoring, in STEM learning design discussion. Thirty-three pre-service teachers enrolled in an online training program, and completed 12 learning design activities with a directive tutor or a facilitative tutor. We collected quantitative data to analyze pre-service teachers' evaluation of training and tutor under two different tutoring styles, and conducted epistemic network analysis (ENA) to analyze 9896 utterances. The findings revealed that there are no statistically significant differences in training satisfaction and perception of learning support between directive and facilitative tutor, while the discourse analysis results show that there is a significant difference in epistemic network and trajectory of preservice teachers. The findings would shed light on how tutor can better stimulate productive discussion in STEM learning design, and how to scaffold high-quality learning design.