The two-dimensional，two-phase seepage problem in dual-porosity medium is hard to derive its analytical solution when the imbibition effect of fracture-matrix was considered. By introducing the concept of travel of time（TOF），the two-dimensional，two-phase problem is simplified into a one-dimensional，two-phase problem. Along the streamline，the characteristics method can be used to solve the analytical solution of dual-porosity medium. Taking the five-spot well pattern for example，the effect of imbibition of fracture-matrix on the water flooding development in the dual-porosity medium was analyzed，and the calculation methods of saturation distribution for homogeneous and heterogeneous reservoirs were given respectively. Research results shows that the advance speed of water flooding front in the dual-porosity medium is fast，and the water breakthrough quickly occurs in production well in the dual-porosity medium. However，the water cut increas? es slowly after water breakthrough because of the existence of imbibition effect. The crude oil in the matrix system is recovered by the imbibition effect of fracture-matrix，therefore，water flooding is an effective method to develop fracture-pore carbonate reservoirs. The research results provide an effective analytical model for the research on the development characteristics of water flooding in the dual-porosity medium.