Emergency medical services are an essential element in the modern healthcare system. Health care services are the most important because they play an important role in saving people's lives and reducing rates of mortality and morbidity. Especially during the covid-19 pandemic and the new normal era makes this problem very interesting to discuss. For this reason, this study tries to overcome the problem location and allocation of Emergency Medical Services (EMS) by using a combination of metaheuristics and simulation. The approach taken to overcome these challenges is developing Symbiotic Organisms Search algorithm and then use the simulation method to validation the result. The transition of the ambulance system from a centralized to decentralized system by using the Modification of Symbiotic Organisms Searrch (Mod-SOS) algorithm, found that to shorten the response time to 9 minutes, need to combine the 5 core bases with about 12 potential bases. From the simulation scenarios tested, the total number of ambulances involved in the proposed system is 16 units. So it can be concluded that involving several potential bases can produce a short response time.