In order to obtain good water plugging effect in high temperature horizontal well with long perforation section and high permeability channel，a depth cross-linking thermosetting phenolic plugging agent was prepared. The gelling，plugging and flood flushing performance of plugging agent at formation temperature（110℃）were studied，and pilot test was carried out at Chu 28-P1 well. The experiment results showed that the plugging agent was homogeneous transparent and low viscous solution，and kept stable at the temperature lower than 80℃ . The effect of formation shearing，adsorption or chromatographic separation on the composition and gelling performance of plugging agent could be ignored. The delayed gelling time was shortened with the increase of temperature，which could be controlled between 12 to 48 h when the temperature was higher than 85℃ . Heated sand pack experiment indicated that the blocking ratio of cured agent kept stable to 96% even after flushed with large amount and high pressure of injected water，showing strong blocking strength and bearing hydraulic push. The gel properties kept stable after aging one year at 110℃ . Field test illustrated the technical advantages of plugging agent，such as being injected selectively to high permeability channel，balancing the formation pressure difference higher than 8 MPa at 110℃，bearing fluid pushing force and suction force generated by negative pressure operation near well.