A polarization-imaging system was developed to measure the two-dimensional diffuse backscattering Mueller matrix of turbid medium. In the system of a polarized,collimated laser beam was focused to a small point on the medium,and the multiply scattered,diffusely backreflected light around this point was recorded with a CCD camera. The system and the theory of measurement were described in detail in the paper. And then,the specular reflecting Mueller matrix of the non-polarizing beamsplitter and the two-dimensional diffuse backscattering Mueller matrix of a 1.5% Intralipid solution were measured. The result confirms that the system can avoid the specular reflectance of the sample and exactly measure the Mueller matrix of the sample.