The invention discloses a method for preparing a single or dual-alkyl substitution product of propane diamine. According to the method, single or dual-alkyl substituted tetrahydropyrimidinone serving as a raw material is hydrolyzed with concentrated hydrochloric acid in the presence of aluminum trichloride to obtain corresponding alkyl substituted propane diamine. The single or dual-alkyl substitution product of propane diamine prepared by adopting the method is high in purity; and the problem of difficulty in controlling the substitution quantity by single alkylation is avoided, and an asymmetric alkyl substituted propane diamine derivative can be obtained with high yield.