In view of the complex downhole conditions of YR1 geothermal well， such as large amount of fault type circulation loss， high water head of the fault water， an openhole interval in the upper part， and taking into account of the application conditions and limitations of the existing plugging technology for malignant circulation loss， it was decided to adopt casing to seal off the fault with analysis of the nature of circulation loss and the borehole environment. The method successfully solved the fault type circulation loss plugging difficulty. In addition， the staged cementing process was adopted to prevent upward channeling and downward seepage of the fault water to ensure the quality of well completion， providing a good reference for dealing with fault or cave type circulation loss in the future. Field practice shows that the casing plugging measure introduced in this paper has the advantages of short operation time， low cost and good effect. The method has facilitated the development and utilization of geothermal resources， and helped to build the “Yuncheng Model”. It has contributed to the local economic and social development and is of great significance to help to campaign against pollution.