The invention relates to method of preparing secondary functionalization organic modified montmorillonite (TFC), toughening and reinforcement biodegradable polylactic acid nano composite material using the organic montmorillonite and preparing method thereof. The novel double-function group organic modified montmorillonite (TFC) enhances adhesion force between montmorillonite and polymer molecule and obviously increases property of the composite material. The toughening and reinforcement biodegradable polylactic acid nano composite material is prepared by using polylactic acid as main raw material, and adding certain poly(epsilon-caprolactone) and lactic acid-epsilon-caprolactone copolymer; plasticizer selects acetyl tri-n-butyl citrate, tri-n-butyl citrate, triethyl citrate, dioctyl phthalate, and dibutylphthalate; lubricant selects aluminum stearate and calcium stearate; heat stabilizer selects maleic anhydride and epoxy soybean oil (EOS); and intensifier selects TFC montmorillonite (MMT). The prepared composite material possesses high strength and good toughness, and is hopeful of replacing traditional non-degradable material to be applied in field such as packaging, medical, and engineering for solving environment problems generated by white pollution.