A new kind of photonic crystal cross waveguides with defect structure is propesed. The transmission characteristics are simulated by finite difference time domain method (FDTD). The obtained results show that the spectrum line-width of transmitted light through the photonic crystal waveguide containing defect structure is much narrower than that in the prototype waveguide without defect structure. This waveguide possesses narrow band filtering function. When the defect medium refractive index is increased, the center frequency of the transmitted spectrum decreases linearly. When the diameter of defect medium center pillar in increased, the center frequency of the transmitted spectrum is reduced. It is expected that this type of defect photonic crystal wave guides may serve as new narrow band filter,light splitter and tunable frequency selector.