In order to study the grating diffractive field's characteristics of the partially polarized and coherent beams, an analytic expression of polarization degree and angular correlation of partially ploarized and coherent beams through polarized gratings is derived based on the beam coherentce-polarization (BCP) matrix approach of partially coherent beams. And then the partially polarized and coherent Gausian-Schell beam (PGSM) is taken as a numerical example to study the influence of the polarized grating TE and TM complex transmission and some parameters of the incident PGSM on the polarization degree of the diffraction field and the diffractive orders's angular correlation in details. It is shown that the PGSM's diffractive field is an uneven and periodically changed partially coherent field, and the symmetrical diffraction order's angular coherence is equal and decreases to zero along with the increase of diffraction orders.