In order to understand the reaction mechanism of TAT from DAPT, N-hydroxymethyl tertiary amines were prepared with secondary amines and formaldehyde as starting materials.The effect of ammonium nitrate on acetolysis reaction of N-hydroxymethyl tertiary amines was also studied.Results show that the acetolysis reaction occurres via N-attack instead of O-attack, then the N-hydroxymethyl is removed to obtain N-acylated product.Preparation of TAT was accomplished by hydrolysis and acetylation of 7-acetoxymethyl-1, 3, 5-triacetyl-1, 3, 5, 7-tetraazacyclooctane, which was converted from DAPT.The acetolysis reaction can be deactivated by nitrate, which is obtained from secondary amine and nitric acid, which is generated by acetolysis reaction of ammonium nitrate.The acetylation yield reduces 18%-41% in the presence of ammonium nitrate.