We proposed a wide spectrum and rapid calculation model FALTRAN（ Fast Atmospheric Limb TRANsmission）

to solve the problems of current radiative transfer model in limb remote sensing. In FALTRAN:（ 1） Band model algorithm was employed and the molecular spectroscopy database was based on HITRAN2008.（ 2） Limb radiative transfer equation consists of scattering and thermal radiation was established

and according to the limb geometry characteristic

a Hemisphere Radiation Adding（ HRA） approach based on finite difference method was proposed to solve it. We investigated the atmospheric limb radiations under typical atmospheric modes in several commonly used remote sensing bands. Moreover

radiation contribution by two hemispheres was quantitative analyzed as well. Validation results show that the relative differences between FALTRAN and Combining Differential-Integral（ CDI） model are within 2%

and calculation results by FALTRAN have good agreement with Michelson Interferometer for Passive Atmospheric Sounding（ MIPAS） measurements. FALTRAN is proven to be reliable in the limb radiative transfer calculation.