[Objective] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with viscosity method and gel permeation chromatography(GPC) method.[Method] In viscosity method,cadmium ethylenediamine was used as the solvent,intrinsic viscosity η of the solution was determined at 25 ℃ by using a Ubbelohde viscometer,to calculate the molecular weight of cellulose;in GPC method,8% LiCl /N,N-dimethylacetamide(LiCl/DMAc) was used as the solvent and 0.5% LiCl/DMAc was used as the mobile phase to determine the relative molecular weight and distribution of cellulose and cellulose microspheres.In addition,the determination results were analyzed to compare these two methods.[Result] Viscosity-average molecular weight Mη of cellulose and cellulose microspheres determined with viscosity method were 224,532 and 16,686,respectively;weight-average molecular weight Mw of cellulose and cellulose microspheres determined with GPC method were 284,196 and 22,345,respectively.[Conclusion] The determination results of GPC method are relatively close to the actual value and could truly reflect the characteristics of molecular weight distribution of cellulose and cellulose microspheres. [Objective] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with viscosity method and gel permeation chromatography (GPC) method. [Method] In viscosity method, cadmium ethylenediamine was used as the solvent, intrinsic viscosity η of the solution was determined at 25 ° C by using a Ubbelohde viscometer to calculate the molecular weight of cellulose; in GPC method, 8% LiCl / N, N-dimethylacetamide (LiCl / DMAc) was used as the solvent and 0.5% LiCl / DMAc was used as the mobile phase to determine the relative molecular weight and distribution of cellulose and cellulose microspheres. In addition, the determination results were analyzed to compare these two methods. [Result] Viscosity- average molecular weight Mη of cellulose and cellulose microspheres determined with viscosity method were 224,532 and 16,686, respectively; weight-average molecular weight Mw of cellulose and cellulose microspheres determined with GPC method were 284,196 and 22,345, respectively. [Conclusion] The determination results of GPC method are relatively close to the actual value and could indeed reflect the characteristics of molecular weight distribution of cellulose and cellulose microspheres.