Abstract　

    The cosmic microwave background (CMB) plays an important role in the radiative transfer of dust and gas emission, especially for the high redshift systems. As the CMB temperature increases with redshift, the CMB temperature can reach to the dust temperature or even exceed the intrinsic dust temperature at high redshifts. Two effects are essential but often be neglected for sub-mm observations: CMB heating on the cold dust, and the background subtraction in submm observations. Combining with these two effects and simple toy models, we discuss the influence to the submm measurement of fluxes and sizes of galaxies at high redshifts.