Abstract: The synthetic method of 4,4'-tetramethyldiaminodiphenylmethane has been improved using oxalic acid and hydrochloric acid as catalysts. The Optimum reaction conditions of the synthesis are: (1) the molar ratio of N,N-dimethylaniline to formaldehyde: 1.7: 1, (2)weight of oxalic acld and hydrochloric acid:74% and 14% to the weight of N,N-dimethylaniline,respectively and (3)reaction time: 3 hours.