Abstract: Using the measured rain attenuation data for terrestrial lineofsight path and earthspace path in ITUR SG3 database, the inconsistency is analyzed between the path adjustment factor derived from rain attenuation physical model based on cylindrical rain cell and the measured rain attenuation data. On the basis of the above analysis, a new rain attenuation physical model is derived base on exponential rain cell (so called EXCELL), in which a new conception of rainfall rate adjustment factor is proposed with theoretical analysis. The main characteristics of the measured rain attenuation data can be explained with this new adjustment factor, which shows that the new rain attenuation physical model is more reasonable. Furthermore, the rainfall rate adjustment factor can be used to provide theoretical basis for modeling rain attenuation prediction both for terrestrial lineofsight path and earthspace path.