[en] Highlights: • The different synthetic routes of 1-Methyl-2,4,5-trinitroimidazole (MTNI) was studied in detail by using DFT method. • The nitration reaction path is affected by the solvent molecule. • The yield is affected by the different nitration mechanisms. During the synthesis of 1-methyl-2,4,5-trinitroimidazole (MTNI), the product yield was affected by group introduction order. This phenomenon has not been explained in the reaction mechanism. In this paper, the DFT method was used to study the synthesis mechanism. For the nitration reaction, an N-H$\cdots$O hydrogen bond was formed between the midazole ring and water molecule in the solution to promote the nitration reaction, so the nitration mechanism was affected by the introduction of methyl group at the N site. For the methylation reaction, the electrophilic attack of the methyl group was affected by the introduction of more electron-withdrawing nitro group.