It is presented that the numerical experiments about effect of the deviation of crustal model used in location on determining focus. Which results show that the model errors affect mainly the depths determination of shallower earthquakes in upper crust, whereas their effect on events in lower crust is few. The shocks determined will be deeper than that of actual ones when model used in location is simpler than that of true structure, on the contrary, the real depths will be deeper than that located. The deviation of total crust thickness will make focu depths calculated a system error which is in close proximity to the thickness deviation. Depths determined with a common model contain the relative accuraty, otherwise they is imcomparable. Finally, the experiment results is discussed briefly.