A green process of synthesizing polyimide from phthalic anhydride and 4,4'-diaminodiphenyl ether monomer was studied. First, polyamic acid was formed between PMDA and ODA in N,N-dimethylformamide DMF solvent. And then, imidization of the polyamic acid was realized synergistically with urea-choline chloride deep eutectic solvent（DES）as both catalyst and solvent, and acetic anhydride as dehydrator. The obtaining high molecular weight product PI could be isolated by a simple and direct filtration. The products were characterized by FT-IR, TGA-DSC, and element analysis, respectively. Also, the effect of reaction temperature, reaction time, DES catalyst dosage and acetic anhydride adding amount on the imidization of PAA was investigated, respectively. Experimental results indicate that under the conditions of 80 ℃, volume ratio of DES to acetic anhydride1：2, molar ratio of PAA to DES 1：2, PI product yield and imidization degree reached an optimal value. the thermogravimetric curve of the prepared sample is close to that of polyimide reported in the literatures, and its infrared absorption spectrum is consistent with specific absorption peak of imide bond reported in the literature. In addition, the DES and DMF showed good reusability. The process is green and do not use such harmful imidization catalyst as pyridine, imidazole and isoquinoline etc.