The invention discloses a preparation method of a composite crosslinked type I collagen membrane. The method includes the steps of: firstly subjecting type I collagen to dissolution stirring in an acid solution in a reaction kettle for 12-24h, then adding a defoaming agent into the solution, conducting stirring for 20-60min, then pumping the solution into a storage tank, and conducting static defoaming; conducting inspection to ensure that defoaming reaches the requirement, then pumping the solution into a film casting machine, carrying out film casting, then performing drying, dipping the film into a first cross-linking agent solution or placing the film under cross-linking conditions for 12-24h, and conducting cleaning, then dipping the film into a second cross-linking agent solution or placing the film under cross-linking conditions for 12-24h, and then performing cleaning and drying; and finally, conducting forming processing, packaging and irradiation, thus obtaining the composite crosslinked type I collagen membrane. The membrane material has good mechanical properties, hydrophilicity, antimicrobial activity and biological compatibility, the degradation rate is controllable and can reach long degradation time, also the preparation process is simple, the equipment is simple, the raw materials are cheap and easily available, and the composite crosslinked type I collagen membrane can be widely used as medical wound dressings, tissue engineering scaffold materials and the like in the medical field.