The invention provides a Schiff base iron compound, a preparation method thereof and application of the Schiff base iron compound as a catalyst. The Schiff base iron compound has a structure represented by a formula (I) (shown in the description), wherein Y represents 1,2-ethyl or 1,2-propyl; and R represents one of -H, halogen and alkyl. The Schiff base iron compound provided by the invention has NNOO four-tooth coordination capacity and can form a metal active central bonding site so as to obtain a tetracoordinated Schiff base iron catalyst. The Schiff base iron compound is utilized for catalyzing ring opening polymerization of lactide and caprolactone, and the catalysis activity is very high; and meanwhile, the Schiff base iron compound has considerable selectivity to racemic lactide, so that the regularity of a microcosmic chain structure of a polymerization product is improved. Experiments show that the yield of polylactic acid prepared by virtue of the method provided by the invention can reach 90%, and the yield of polycaprolactone can reach 96%; and when lactide is racemic lactide, the stereoscopic regularity (Pm) of obtained polylactic acid can reach 0.60.