Advanced glycation end products(AGEs) are largly involved in the pathogenesis of diabetic nephropathy. It is obvious that inhibition of AGEs formation is important in preventing the occurrence and progression of diabetic nephropathy. In diabetes, this reaction is greatly accerated and is important in the pathogenesis of diabetic complications, especially diabetic nephropathy. Therefore, to seek possible AGEs inhibitors in herbal medicines, unprocessed - and processed Magnolia Bark were examined in vitro as basic data for aniaml experiment. The content of magnolol in unprocessed Magnolia Bark was 0.796±0.072%, and after processing was decreased to 0.586±0.101%(p<0.01). The content of AGEs was measured by their intrinsic fluorescence. The IC_50(㎍/ml) values of aminoguanidine, unprocessed- and processed Magnolia Bark are 38.845±8.36㎍/ml, 54.264±3.153㎍/ml and 27.882±1.836㎍/ml, respectively. This result means that processed Magnolia Bark was more effective than aminoguanidine, as positive control.