The invention relates to the field of preparation of fibers, in particular to a cotton stalk processing technique and a cotton stalk bast fiber preparation technique. The cotton stalk processing technique comprises the steps of mixing cotton stalk bast fiber and plasma-state degumming liquid, bleaching, softening, and drying, wherein the degumming liquid is mainly prepared from, by weight, 2-5 parts of an inorganic base, 1-3 parts of a sodium salt, 2-6 parts of pectinase, 3-5 parts of beta-glucanase, 3-5 parts of metalloproteinase and 1-3 parts of papain. The cotton stalk processing technique enables cotton stalks to be processed quickly and efficiently to obtain cotton stalk bast fiber having complete fiber structure; the cotton stalk processing technique is simple to perform and has no need for repeated operations.