The invention provides a microcrystalline cellulose modified polypropylene composite film and a preparation method thereof and belongs to the technical field of packaging materials. The microcrystalline cellulose modified polypropylene composite film at least comprises two layers. At least one surface layer is a nano-scale microcrystalline cellulose modified polypropylene layer, and the other layers are polypropylene layers. The preparation method includes the steps of preparation of an NCC master batch and preparation of an NCC modified polypropylene film (CPP). The compound performance of the composite film is improved, and the Young modulus, gas barrier property and heat resistance of the film are obviously improved.