Abstract: Dinitro pentamethylene tetramine (DPT) is an important precursor of octogen (cyclotetramethylene tetramine, HMX). This article explores the process of synthesizing DPT by one-pot method to provide a practical basis for improving HMX production through DPT. The urea was used as the original material. Without isolation from intermediates, DPT was obtained by the chemical reaction of nitration, hydrolysis and Mannich condensation. Some factors to affect yield of DPT were investigated, such as dosage of nitric acid, nitration time, hydrolyzation time, dosage of formaldehyde, pH of solution and so on. The optimum conditions of process were determined. With this process, the yield of DPT was advanced up to 65.2%.