The invention discloses a power supply optimal configuration method for a sea island type micro-grid. Firstly, each referred power supply in the micro-grid serves as a particle, referred power supplies of various types in the number xi serve as a group of particles, and a particle swarm is established; construction cost at the beginning of a planning period, the electric quantity Eti generated within the planning period, generated fuel cost Oti and operating maintenance cost Mti of each group of particles are obtained; secondly, whether the construction cost, the electric quantity Eti, the fuel cost Oti and the operating maintenance cost Mti meet set constraint conditions or not is judged, and if the construction cost, the electric quantity Eti, the fuel cost Oti and the operating maintenance cost Mti meet the set constraint conditions, fitness of the particle swarm is calculated through a current objective function; if the construction cost, the electric quantity Eti, the fuel cost Oti and the operating maintenance cost Mti do not meet the set constraint conditions, the fitness of the current particle swarm is adjusted by the adoption of a penalty function, and the optimal particle group is picked out according to calculation of the fitness of the particle swarm; after the optimal particle group is picked out, the optimal solution is outputted until set iterations are achieved, and thus power supply optimal configuration of the sea island type micro-grid is obtained. An algorithm of the particle swarm is adopted to solve most preferably power supply optimal configuration capacity, so investment cost of the micro-grid within a full life cycle is reduced, and stability of the micro-grid is improved.