The invention relates to a novel sectional type process which extracts cellulose from plant bodies, and comprises the following steps: the process is that dilute alkali is first used for soaking the plant bodies, and then pressurizing, steaming, polishing and pulp washing are carried out so that the cellulose is obtained. The sectional type process has the advantages that very dilute alkali can be used for soaking or evaporating the plant bodies, not only the amount of alkali is greatly saved, but also the heating temperature is reduced, the heating time is shortened, the cellulose can be obtained at yield coefficient, and the secondary pollution brought by using sulfide, anthraquinone and other high pollution auxiliary agents is avoided. The soak solution and the cleaning solution can be used together in a cycling way, so liquid or solid organic fertilizer with high concentration can be conveniently obtained.