Aiming at the problem of recycling scraps unsymmetrical dimethylhydrzine (UDMH), eight saturated aliphatic aminimides with low melting points were synthesized after UDMH was alkylated, acidylated and dehydrogenated. The structures, melting points and pyrolysis activities of aminimides were studied. FTIR spectra show that the resonance structure N=C—O^- and N^-—C=O is formed resulting from delocalization of the electron pair in the p-orbital of the imide nitrogen with the π-orbital of the carbonyl. The positions of the characteristic absorption peak frequencies of the two resonance structures are influenced obviously by the inductive effect of the substituent in carbonyl. The carbonyl substituent with a weaker inductive effects cause the IR absorption peak to shift toward higher frequencies. Dynamic DSC results show that the carbochain of amine group presents a little effect on the pyrolysis activities of aminimide among the aliphatic saturated aminimides. The aminimide with a longer carbonyl carbochain presents higher pyrolysis activity.