Intensity dependent absorption in doped KNSBN crystals have been studied. Light induced absorption and transparency in Co:KNSBN and heavy reduced Co:KNSBN have been experimentally measured. Light induced absorption increases and reaches a saturate value of 6.5 cm -1 in heavy reduced Co:KNSBN crystal. Light induced absorption decreases and reaches a saturate value of 3.2 cm -1 in Co:KNSBN crystal. The transparent intensity of probe beam present a oscillation behavior when the pump beam switch off in heavy reduced Co:KNSBN crystal. These behaviors are explained by a theory of two types of charge carriers with multiple traps. Finally, we predict that the light induced absorption and transparency should be useful for making spatial intensity distributions more homogeneous and incoherent signal amplification.