Background: Ambulance cardiopulmonary resuscitation (CPR) performed during transport in a scoop and run Asian emergency medical service (EMS) system has known to be associated with poor quality in CPR and unsafe for EMS providers. We developed a CPR jacket attaching a safety belt and a CPR feedback device and tested the effect of the jacket on quality of CPR and safety for EMS providers. Methods: The CPR jacket we developed has three units; 1) a basic jacket, 2) a safety belt to be easily linked and detached to the bar of stretcher cart during ambulance transport, and 3) a watch-like visual feedback device wearing on a provider`s hand (Fig. 1). A simulated cross-over randomized controlled trial was performed with a scenario of ambulance transport which had three driving courses (acceleration, curve, and deceleration) among total travel distance (3.1 km) under the speed of less than 40 km/hr. Total 24 emergency medical technicians were recruited and randomized with standard CPR group (S-CPR) and jacket CPR group (J-CPR). Primary outcome was quality indicators; appropriate compression depth rate (>5 cm depth), place, and decompression monitored by a simulation monitoring manikin (Skill Reporter, Laerdal). Secondary outcome was the number of accidental collision/ fall-down of EMS provider recorded by a camcorder. We compared the outcomes between S-CPR and J-CPR. Results: The male of EMT was 12(50.0%) and average age was 26.4 years old. Appropriate compression was significantly higher in J-CPR (23.1%) than S-CPR (10.9%) in deceleration course (p<0.05). Appropriate place and decompression were significantly better in J-CPR (92.0% and 97.3%) than S-CPR (81.2% and 87.7%), respectively (each p<0.05). No significant differences in compression depth were there in acceleration and curve course between two groups. Accidental collision was significantly less in J-CPR than S-CPR (0.3 vs 1.7) (p<0.05). Conclusion: A CPR jacket to provide a safety belt function and feedback monitoring function during ambulance CPR during transport showed significantly higher quality and safety in a simulated controlled trial. Further clinical trials are required to prove the efficiency and safety.