The invention discloses a nutria tail collagen surgical suture and a preparation method thereof. The method comprises the following steps: cutting standby nutria tail tendons into thin pieces, performing enzyme treatment by a ficus proteinase solution, preparing extracted natural collagen into a spinning solution, performing forming through a solution wet-spinning technology, and performing cross-linking to prepare the nutria tail collagen surgical suture which is a continuous long filament. The surgical suture has the diameter of 0.118-0.135 mm, the knot strength of 450-510 g and the elongation rate of 10.1-12.3%. The surgical suture meets the requirements of American suture size 6/0 and is suitable for clinical suturing. Biological experiments and clinical trials prove that the nutria tail collagen surgical suture has various advantages of mild tissue reaction, naturalness, degradability, non-toxicity, stability and reliability for absorption, high tensile strength, no need of being taken out, capability of being naturally absorbed or naturally falling off, no irritation, no scars after wound healing, and the like.