Abstract: Purpose: The article is to tell how to fix the focus' position by CT scan and to Provideaccurate data for both target-setting of X-knife radiotherapy and working up a therapeutic schedule.Method: The article reviews and summarizes the utilization method of the X-knife position-finding under CT scan and its cooperation with high -Pressure injector intreduces in detail the main parameterindexes and the setting of relevant parameters . Conclusion : The position-finding method can show thefocus clearly and protide accurate data. The whole therapeutic procedures can be gone though in a shortperiod and the completeness, accuracy, direct observation, high -efficiency and safety can also byguarantee