In this paper N,N-dimethyl dehydroabietylamine(DDAA) from dehydroabietylamine(DAA) was synthesize based on formaldehydefonnic acid method. By IR、UV and chemical analysis of product(DDAA), its results showed: (1)two N-H spectral bands already disappear within 3550-3320 cm-1 on the IR spectrogram of the DDAA in contrast with IR spectrogram of the DAA; (2)the DDAA picrate had maximum absorption nearby 350 nm on the UV spectrogram of the DDAA picrate; (3)the DDAA content was determined by nonwater-potentiometer-titration in glacial acetic acid-aceticanhydricle-perchloric acid as a standardized solution. The DDAA content was 75%. And this method is feasible in synthesising DDAA.