We investigated spontaneous imbibition behavior in a basic bifurcated channel. The rupture and convergence of the two-phase interface in a bifurcated channel is strongly unsteady, which is hard to be described accurately with classical theories and conventional numerical calculation methods. An improved two-component pseudopotential lattice Boltzmann method was employed in simulating the unsteady spontaneous process. It shows that the width of inlet/outlet channel controls the competitive imbibition behavior in the bifurcated channel. Whereas the viscosity ratio between the wetting phase and the non-wetting phase controls the overall spontaneous imbibition behavior. The results provide a basis for quantitative characterization of spontaneous imbibition in complex pore structures.