The present disclosure relates to a micro-loss combined mechanical DC circuit breaker and its control method, consisting n ports, n load current paths and a main breaker; wherein the n load current paths are parallel with the main breaker, and each load current path is divided into an upper bridge arm and a lower bridge arm at a connection point; each port is electrically connected to the connection point of a load current path; the upper bridge arm of each load current path is made of an ultra-fast mechanical switch; the lower bridge arm of each load current path is made of a residual current breaker and a fast closing switch; the main breaker consists of a high-voltage capacitor in series with a low-voltage capacitor that is pre-charged.