The invention discloses a composite coating agent for aloe gel carried deep submicron Ag and a method of using the composite coating agent for keeping aloe fresh and belongs to the field of fresh-keeping of fruits and vegetables. A synthetic method of the composite coating agent comprises the steps of selecting sodium dodecyl sulfonate and the like as a modifier of Ag, assisting by hydrochloric acid to regulate a pH value, carrying out reaction under the condition of heating and mixing to obtain modified deep submicron Ag, putting the deep submicron Ag, the aloe gel, glycerel monostearte and acetic acid in a magnetic heating mixer, and carrying out mixing and ultrasonic degassing to obtain the aloe gel / deep submicron Ag composite coating agent. With the adoption of the composite coating agent, a composite film can be prepared; after fresh aloe stems and leaves are treated by methods of selection by classifying, impurity removal by cleaning, finishing, slitting, rapid sterilization, coating, packaging and warehousing, the initial colors, the surface elasticity, the moisture and the nutritional ingredients of the fresh aloe stems and leaves can be effectively kept. The composite coating agent, the composite film and the method of using the composite coating agent for keeping the aloe fresh are easy to operate, are high in high performance cost ratio and have a wide prospect.