The present invention relates to a method of manufacturing an agricultural film which is completely biodegradable, comprising the following steps: firstly adding polylactic acid and additive into a reaction tank followed by mixing to carry out modification, wherein the additive contains glycerol, poly-(lactide-co-glycolide) and licorice then well mixing the modified polylactic acid and filler using a pelletizer to produce polylactic acid polymer pellets which is completely biodegradable casting the polylactic acid polymer pellets into a film by using a casting film machine and finally cutting the film according to the specification with a slitting machine to obtain the agricultural film of required specification. The agricultural film of the present invention has lower production costs, can fully replace existing plastic films, and is completely biodegradable within a specified duration as needed.
