The invention provides a fibrin gel-polylactic acid composite scaffold and a preparation method thereof. The preparation method comprises the following steps: obtaining a polylactic acid porous scaffold; carrying out surface activating treatment on the polylactic acid porous scaffold by using sodium hydroxide; and carrying out surface grafting on the surface treated polylactic acid porous scaffold by using sodium polyacrylate; and filling apertures in the surface grafted polylactic acid porous scaffold with fibrin gel. The composite scaffold is obtained through compounding the polylactic acid porous scaffold with the fibrin gel through the preparation method, and the polylactic acid porous scaffold undergoes surface modification and grafting treatment according to target requirements in the embodiment of the invention to improve the endophilicity and cell adsorptivity of the polylactic acid porous scaffold and enhance the water retention ability, so guaranteeing of the form and the effect level of the fiber gel is benefited, and the fibrin gel-polylactic acid composite scaffold has good mechanical performances.