Crystal grains in polycrystalline metals rotate during the plastic deformation by crystal slips, which results in the deformation textures of polycrystalline metals. In the present paper, the rotation of crystal due to slips was calculated adopting the constant stress model of polycrystals. The rate dependent type constitutive laws for crystalline materials that deform plastically by slips was used.Namely, a power law used by Hutchinson and an exponential type law proposed by Bodner were adopted as a relation between shear stress and shear strain-rate on the slip plane. It was pointed out that the parameters in the rate-type constitutive equations are related to the number of active slip systems. The relation between the rotation of crystals and these parameters, that is, the number of the active slip systems was clarified. A method was proposed to change the constant stress polycrystalline model toward the constant strain model by changing the parameter in the constitutive equation.