In response to the Curriculum Guidelines of the 12-year Basic Education, this study strengthens the cultivation of teachers in designing PO+E (Prediction - Observation - more Explanation) experiments and inquiry teaching and compares how graduate students from different backgrounds achieve the effect of teacher education. This study included graduate students in the Department of Natural Science Education at a University of Education, including 7 in-service teachers and 7 non-in-service teachers. This study adopted the "predictive-observation-more explanation (PO+E)" teaching method, with course content that included Introduction to insect physiology, PO+E theory and teaching demonstration, Imitation of experiment design and micro-teaching, and Self-designed experiment and micro-teaching. Research tools include: Assessment of PO+E Design Experiment (APD), Micro Teaching Assessment of PO+E (MTAP), and Assessment of Scientific Explanation Ability (ASE), etc. The results are as follows. 1) Both groups of graduate students could use the PO+E teaching method to design experiments and learning sheets. The non-in-service teachers group was better at selection of teaching material for self-designed PO+E experiments. 2) The in-service teachers group was better than the non-in-service teachers group in terms of MTAP scores for both imitation and self-designed micro-teaching. 3) The ASE scores were similar between the two groups of graduate students, but the in-service teachers group was slightly better. The two groups of graduate students made significant progress on scientific explanation ability in the second stage. 4) For the cultivation of the PO+E teaching method, the in-service teachers group should strengthen the selection of PO+E teaching materials, while the non-in-service teachers group should enhance the teaching ability of micro-teaching. 5) It is suggested that training in-service teachers group should focus on finding PO+E experimental materials, and training non-in-service teachers group should focus on micro-teaching and interaction skills.