Abstract: Effect of energy competition between spontaneous emission and injected seed signal to injection locking master-slave lasers is analyzed.The injected seed laser is a monolithic non-planar single frequency ring laser.The slave laser is a Q-switched resonator with high repetition frequency.Single frequency pulse laser having a pulse width of 40?ns and an output power higher than 5?mJ is obtained.Locking probability is tested under conditions of different frequency, power and pumped energy of the slave laser.It is shown that the frequency matching and pumped energy of the slave laser are the important factors of injection seed probability.