The invention discloses a biological membrane which promotes healing and a preparation method thereof. The biological membrane which promotes healing is prepared by mixing chitosan derivative solution and sesame oil for ionic crosslink and drying the mixture to form membrane. The membrane has a certain flexibility and strength and integral gel can be formed after the membrane absorbs exudates. Adhesion with wound surface can be avoided, thus medicine changing is convenient and no secondary injury is caused. In addition, the membrane has the advantages of moist keeping, antibacterial action, scars reducing and the like. The membrane has obvious curative effect of promoting wound to heal and is applicable to curing surgical wound, bruise, burn, donor site, bedsore, diabetic ulcer and other wound surfaces which are difficult to heal.