Prediction of MW scale and MWD of cellulose by means of a theology-based method is developed. In this method, for the cellulose/NMMO.H2O solution, it is assumed that the cellulose MW values calculated by the Rouse terminal relaxation time can be regarded as the peak MW on the MWD curves of cellulose. Consequently, it is realized that the reciprocal of the frequency is converted to the MW scale, obtaining MWD scale curves of cellulose. Meanwhile, the obtained results are compared with those measured by the GPC method. The comparison shows that the calculated peak MW values are approximately equal, the calculated PDI values and MWD curves have the same trends. Consequently, it may be feasible to compare the MW scale and MWD of cellulose by using the rheology-based method. In addition, the theology-based method is simple and fast. Therefore, it is a useful and easy way to analyze the MW scale and MWD of cellulose in the fiber industry.