Both formative OSCE and OSTE can assess and instruct trainees' competency, skills, and foster experience accumulation. Purpose: This study aimed to evaluate the effectiveness of assessment and training the "emergency care", "call for help timely" and "teaching" skills of PGY residents with formative mini-OSCE+OSTE in modules A or B. Methods: Between February and August 2017, we recruited 42 PGY residents who had completed either three or six months of training (PGY_(3m) and PGY_(6m) residents, respectively). PGYs were randomly divided into groups to receive either module A and B of formative mini-OSCE+OSTE. In module A, every PGY resident rotates three long-stations mini-OSCE+OSTE alone. In module B with the element of peer-assisted learning (PAL), three PGY residents rotate three mini-OSCE+OSTE together in an hour. Results: In the module B cohort, the "emergency care", "call for help timely" and "teaching" skills of PGY_(3m) residents were all better than those of PGY_(6m) resident. In other words, module B (with PAL) revealed the cumulative effects of short- (3-month) or long-term (6-month) training. In particular, the training benefited module B PGY residents more in the development of "emergency care" and "call for help timely" skills. Both module A and B participants reported that their clinical skills were improved by this training. Conclusions: Our study suggested that formative mini- OSCE+OSTE by teams of three PGYs is a feasible model to assess and train participants' clinical and teaching skills.