The Ar+ 514.5 nm laser beam is used at non-simultaneous writing-reading process. As the signal beam is with extraordinary polarization and the polarized direction of the pump beam has an angle Ψ with its extraordinarily polarized direction, the two-wave coupling property of a Ce∶KNSBN photorefractive crystal is experimentally studied. Because of the effect of the fanning, the polarization configuration that both the signal beam and pump beam are with extraordinary polarization is not as optimized as it is expected. As the angle between the signal beam and the normal of the crystal face takes 11the gain of the signal beam reaches its maximum and the fanning noise is depressed greatly. while Ψ=30°, those can be explained that the ordinary component of the pump beam as an incoherent beam erases the fanning and the gain of two-wave mixing is enhanced.