Abstract: It was found that the side-reactions caused by formaldehyde is an important influence factor in the synthesis of glyphosate started from glycine by analysis with 13C NMR, 31P NMR, and 1H NMR. Hydroxymethyl phosphonic acid, Polaris, N-(methylation)glyphosate and phosphite were the main by-products and reducing or restraining the generation of them is the crux of optimizing glyphosate technique. Optimizing the technique of synthesizing glyphosate starting from glycine has great significance in theory.