The analytical expression for the polarization transverse distribution of multi-Gaussian Schell photon beams propagating through the modified von Karman turbulence channel are studied, in consideration with the effects of outer and inner scale of turbulence. It is found that the zenith angle has a very slight effect on the degree of polarization of photon beams. In the area near to the beam center, the degree of polarization increases as the source's transverse size and source's transverse coherent width increases, or sub-beam number M decrease. However, in the area away from the beam center, increasing value of sub-beam number M or decreasing the source's transverse coherent width and the source's transverse size, larger the degree of polarization of beams is achieved.