2,4,6-triethyl-5,6-dihydro-4H-1,3,5-dithiazine was synthesized by the reaction of 0.10mol propional with 0.18mol aqueous solution of ammonium sulfide in ethanol. Its structure was characterized by FTIR, FTMS,1HNMR and 13CNMR. The crude product obtained was analyzed by GC-MS. The analytical result showed that its constituents mainly included 2,4,6-triethyl-5,6-dihydro-4H-1,3,5-dithiazine, 2,4,6-triethyl-hexahydro-1,3,5-trizine, N-propylidene-1-amino-1-propene, 3,5-diethyl-1,2,4-trithiolane, 2,4,6-triethyl-tetrahydro-1,3,5-thiadizine, N,N’-dipropylidene-1,1-propylenediamine and 3,5-diethyl-4,5-dihydro-1,2,4-dithiazole. The formation mechanisms for main product and by-products were speculated. Meanwhile, thermal decomposition process of products, including 2,4,6-triethyl-5,6-dihydro-4H-1,3,5-dithiazine, 2,4,6-triethyl-tetrahydro-1,3,5-thiadizine and 2,4,6-triethyl-hexahydro-1,3,5-trizine, were discussed when they were analyzed by GC-MS. Finally, the safety issues of 2,4,6-triethyl-5,6-dihydro-4H-1,3,5-dithiazines as potential food flavor were evaluated.