The invention relates to a preparation method of green nylon poly butyrolactams, the biological materials of GABA in vacuum under the condition of high temperature melt decomposition and purified butyrolactams, then by vacuum polymerization of green nylon poly butyrolactams. Compared with the prior art, the invention is prepared by biological method for the synthesis of a wide range of sources, to solve the problem of raw material supply PA4 for mass production, reduce the cost of reaction, and the reaction condition is simple, easy to implement simplified synthesis steps, from the laboratory to the transformation of industrial production.