Abstract: Using the isomeric mixture diamine monomer diethyltoluenediamine（DETDA） as the diamine raw material，using the melt polycondensation method，DETDA，4，4'- oxydiphthalic anhydride （ODPA），3，3'，4，4'-diphenylketone-tetrahydride （BTDA） was ternarily copolymerized in different proportions，and after high-temperature thermal imidization，5 kinds of DETDA/ODPA/BTDA molding powder were obtained，of which 3 kinds of molding powder can be dissolved in N，N-dimethylformamide（DMF）and coated to form a film. Then the structure，thermal properties of 5 kinds of molding powders and films were tested. The results showed that these molding powders were easy to process， and the five molding powders and films had excellent thermal properties.

Key words: isomeric mixture, polyimide, ternary polymerization, molding powder, film