The invention relates to an alginate dressing for treating bedsores and a preparation method thereof. The dressing has a double-layer composite structure, that is, it is composed of a bottom layer and a surface layer, the bottom layer is an alginate composite film layer, and the surface layer is a natural rubber film layer ; Its preparation method comprises the following steps: A, preparation of shark collagen solution; B, preparation of coaxial electrospinning outer layer solution; C, preparation of coaxial electrospinning core layer solution; D, spinning; E, crosslinking ; F, impregnation; G, preparation of epoxidized natural rubber film; H, composite. The dressing prepared by the invention has good biocompatibility, controllable growth mediation of synthetic biological materials, good hygroscopicity, anti-inflammatory and antibacterial properties, can improve local blood supply of wounds, promote tissue growth, and accelerate wound healing, showing It has good versatility, good porosity, soft and comfortable hand feeling, good compliance, easy to use, and is suitable for use in the field of modern biomedicine, especially in the fields of bedsore treatment and care.