It is necessary to foster teachers' ability to design and implement instructions that encourage students to construct evidence and engage in argumentative discourse. The argument of this paper is that the continuous reflection and discussion as well as regular practice on instructional designs will promote pre-service science teachers' (PSSTs') competence to guide students in providing evidence. An in-depth analysis on PSSTs' instructional designs provided evidence for this argument. For this purpose, this study implemented an action research (AR) in which PSSTs' instructional designs were analyzed before and after the three-week reflection and discussion on instructions that they conducted in groups of three or four in a science education course. The author of this paper, who is also the instructor of the course, analyzed these instructional designs to identify PSSTs' level of guidance by using the rubric that she created with expert judgment. Two other researchers and the author coded each category in the rubric independently. She scored the PSSTs' level in each category from 1 to 3 and then calculated their total score for the design. She also made paired samples t-test on the scores of each category and in total scores to identify how the PSSTs' instructional design guides students to use evidence before and after the continuous reflection and discussion of their instructional designs. The results suggested that integrating continuous reflection and discussion into her teaching improved PSSTs' guidance in providing evidence. Concluding remarks will be made for the further implications of this study.