Preparation method of biomass cellulose nanofibers with high length-diameter ratio

The invention relates to a preparation method of biomass cellulose nanofibers with a high length-diameter ratio, in particular to a preparation method of nano cellulose fibers, solving the problems that nano cellulose fibers prepared by using a traditional method for hydrolyzing biomass cellulose with strong acid have short length and small length-diameter ratio, nano cellulose fibers prepared byusing a mechanical shearing method are easy to mutually aggregate, and a microbial fermentation method has high cost. The method comprises the following steps of: (1) purifying biomass cellulose witha benzyl alcohol solution; (2); treating with acidified sodium chlorite; (3) treating lye; (4) treating with the acidified sodium chlorite again; (5) treating with KOH; (6) treating with hydrochloricacid; and (7) ultrasonically treating and drying to obtain biomass cellulose nanofibers with high length-diameter ratio not less than 1500, fiber diameter from 50 nm to 300 nm, length not less than 150 um and length-diameter ra