Solution properties of celluloses from different biological origins were investigated in terms of rheological properties in 8 wt% LiCl/amide solutions. The solution viscosities were proportional to the α-th power of the polymer concentrations. The exponent, α, was 3, 4, and 7.5 for the solution from bacterial, wood and cotton, and tunicate cellulose in the semi-dilute regions, respectively. These celluloses were blended to get solutions having various molecular weights and molecular distributions of the polymer. The high molecular weight component, tunicate cellulose: M w=4.13×106, had remarkable effect on the long-time region of the viscoelastic functions of the blends. The weight fraction dependence of the zero-shear viscosity of the blends can be expressed by a linear mixing relation based on Ninomiya theory. The zero-shear viscosities of the blends are proportional to the 5/2-th power of the weight-average molecular weight calculated from a linear combination of that of each component. This indicates that the zero-shear viscosity of the cellulose blends depends strongly on the molecular weight and scarcely on the molecular distribution.