This paper presents a study on the influences of timing, injected signal power and injected beam diameter upon the output power and divergency of a injection locking system, which is composed of two similar telescope unstable OVL with a 45° glass plate inside of one laser as coupling optics. The results showed that the injected signal strongly suppressed the competition of high order transverse modes (including ASE) in cavity, then led to raise the efficiency and to improve the divergency simutaneously. In the case of output power about 5W, the injootion locked system raised the power by 30%~40% and reduced the divergency to half, compared with the independent unstable reaonator.