In view of the leakage control problem of cement sheath in Tahe oilfield，the liquid channeling sealing agent was prepared by mixing 2-acrylamide-2-methylpropane sulfonic acid and acrylamide coploymer （AM-AMPS） with phenolic prepolymer which was synthesized from formaldehyde and phenol. The structure of phenolic prepolymer was characterized by infrared spectrometer and mass spectrometry. The effects of the concentrations of polymer AM-AMPS and phenolic prepolymer，and temperature on the curing of channeling sealing agent were studied，and the stability of channeling sealing agent was evaluated. The results showed that the when the molar ratio of formaldehyde to phenol was 2.8∶1 and the pH value of the system was 8—10，the synthesized phenolic prepolymer was a resole phenolic with 2—3 degree of polymerization. The mass fraction of hydroxymethyl formaldehyde and free formaldehyde was 36.1% and 0.03% respectively. Appropriate amount of AM-AMPS could increase the cementation ability between phenolic prepolymer and pipe wall，and improve the breakthrough pressure gradient of channeling sealing agent. The main reaction of channeling sealing agent（0.5% AM-AMPS+40% phenolic prepolymer）was curing reaction at 140℃ . The breakthough pressure gradient after curing was 150.6 MPa/m and the cruing time was 37 min. The strength of channeling sealing agent after curing increased with increasing amount of phenolic prepolymer，and was less impacted by temperature. Temperature was the main factor affecting the curing time of channeling sealing agent. The channeling sealing agent had good stability under high temperature（90—140℃）and high salinity（100—240 g/L），which could be used to seal channel and plug leakage in Tahe oilfield.