The squeezing properties of light field in the process preparing Raman-type atom laser via stimulated Raman transition of the Sodium atom Bose-Einstein condensate（BEC） interacting with two light beams, a weaker squeezed coherent probe light and a stronger classical pump light, are studied. The results show that the squeezed coherent probe light can be periodically squeezed. The squeezing period of the probe light is related to the mean number of atoms in trap, the strength of interaction between squeezed light and BEC atoms, and the detuning of the light, and the squeezing depth is determined by the initial squeezing factor of the probe light.