▎ 摘　　要

NOVELTY - Preparing modified polylactic acid material comprises mixing the modified nanocellulose and lactic acid in water to obtain a mixed dispersion, and the modified nanocellulose has a sulfonic acid group and a hydroxy group, heating the mixed dispersion and stirring until the solid content of the mixed dispersion is 80-95% at 140-180degrees Celsius and the pressure of 2-6 kpa for 1-12 hours in-situ catalytic melt condensation polymerization reaction, removing the separated moisture from the reaction system to obtain a nanocellulose polylactic acid prepolymer composite material, pulverizing the nanocellulose polylactic acid prepolymer composite material to obtain powder, keeping the powder at 70-120degrees Celsius for 0.1-5 hours, subjecting to solid phase condensation polymerization for 0.1-20 hours at 120-160degrees Celsius and a pressure of less than or equal to 2 kpa. USE - The modified polylactic acid material is used as nucleating agent, toughening agent or plasticizer of polylactic acid for preparing polylactic acid composite material (all claimed). DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: modified polylactic acid material prepared by the above-mentioned method; preparation polylactic acid composite material, comprising blending polylactic acid with the modified polylactic acid material.