An all-fiber coupling loop is constructed by three 2×2 fiber couplers according to certain rules, which connects three independent erbium-doped fiber lasers to form a coupled array. Thanks to the specially designed all-fiber coupling loop, the total loss of the phase locking array is reduced remarkably, and effective mutual injection coupling occurs between the component fiber lasers, so that the phase locking of the array is achieved. The far field interference patterns and output spectrum observed in experiment indicate that the array has achieved phase locking states. When the pump power of three component fiber lasers is 100mW each, the phase locking array gives 94mW stable coherent output.