Polarized brightness temperature（TB）data of the DMSP SSM/I over crop areas of the northern China in 1996 is studied. Some TB indexes

such as scattering

polarization and crop monitoring indexes

are defined and applied to the analysis of temporal variation of thermal emission from crop areas. This paper provides a novel approach to analyze the functional dependence of polarized microwave TB data on atmospheric and surface conditions during crop growth. It also presents a numerical simulation of vector radiative transfer equations with multiple scattering for a vegetation/snow model at SSM/I channels.