The invention belongs to the field of pharmaceutical material and particularly relates to a medical cassava starch composite film prepared by the compounding of cassava starch and a preparation methodthereof; and the preparation method comprises the following steps: simultaneously weighting cassava starch, polyvinyl alcohol and crosslinking agent according to a certain proportion, then dissolvingseparately, mixing the raw materials, spreading film, crosslinking, removing impurities and loading drugs to prepare the medical cassava starch composite film. The composite film of the invention haswide sources of raw materials and cheap price; cassava starch and polyvinyl alcohol are crosslinked to prepare the reinforced and toughened starch composite film so that the composite film has good biocompatibility, drug-loading property and degradability and higher wet strength; and the film can be used for the coating of body surface traumas, burns and the like and the used waste material can be fairly rapidly degraded so that the medical cassava starch composite film can be utilized to develop a kind of environmentally protective medical film material and has better development potential.