In this paper, the effects of stress state and loading time on deformation resistance of fresh mortar are investigated quantitatively, and the relational formulas between shearing strain rate and shearing stress, mean principal stress as well as loading time are induced by applying the mechanical constitutive law which the authors have already proposed on the assumption that fresh mortar is a kind of particle assembly. Moreover, the formulas for calculating apparent viscosity are given, which is defined as the ratio between shearing stress and shearing strain rate. As the results, (1) Shearing strain rate becomes higher with the increase of shearing stress in each stress state. (2) Shearing strain rate drops off with loading time in visco-elastic state and visco-elasto-plastic state, but increases in failure state. (3) Shearing strain rate decreases with the increase of mean principal stress in each stress state. And these results are verified by a series of shearing tests using mortar which is in from dry state to high flowing state.