The invention discloses a method for accelerating cornstalk field returning decomposition. The method comprises the following steps of regulating the moisture content of sawdust; putting the sawdust into a fermentation tank; then, covering flannelette onto the upper surface of sawdust at the top layer; performing fermentation for 5 to 7 days to obtain fermented sawdust; crushing cornstalks; mixing the cornstalks with the fermented sawdust according to a mass ratio being 4:(1 to 2); after the sufficient and uniform mixing, piling the materials together; performing natural condition fermentation until the cornstalk decomposition requirements are met; obtaining cornstalk decomposition substances; spraying inhibiting agents into the cornstalk decomposition substances; performing placement for 2 to 3 days to obtain the decomposed cornstalks used for field return. The method has the advantages that cellulose substances in the cornstalks can be degraded by various enzymes contained in hyphae grown from the sawdust; the surface structure of the stalks can be damaged; the stalk degradation can be accelerated, so that the cornstalk decomposition efficiency is greatly improved; the effective path is provided for the crop stalk field return utilization.