In order to improve the contradiction between low viscosity and high strength of epoxy water plugging agent in oil and gas fields，a low viscosity and high strength material used in gas field plugging agent was prepared with bisphenol F epoxy resin（B）as matrix，n-butylated phenolic resin（BPF）as crosslinker and diluent，and 2-ethyl-4-methidazole（EMI）as accelerant. The structure of BPF and its effect on the viscosity，curing time and mechanical strength of the system were studied. The results showed that the viscosity of the curing system could be significantly reduced by the addition of BPF. When the mass fraction of BPF reached 80%，the viscosity of B/BPF system was 50 mPa·s，which completely met the need of its transportation to the depth of gas field. EMI could obviously promote the curing of the system and shorten the gelation time. By adjusting the content of EMI，the curing time of the system could be adjusted within 1—7 h. B/BPF system had high crosslinking density，which endowed the system with excellent mechanical property，and its compression strength was up to 129 MPa. In addition，B/BPF system had decent water/acid resistance and thermal stability，and could stably exist for a long time under the harsh conditions of high temperature and high salinity. B/BPF plugging agent had low viscosity before solidification and high strength after solidification，which met the application requirement of water plugging agent for gas well.