Four kinds of diallylmethylalkyl(C12,C14,C16,C18) ammonium bromide were synthesized by using diallylmethylamine and 1-bromoalkane straight chain alkanes as raw materials.The effects of reaction temperature, reaction time, molar ratio of raw materials and solvents type on product yields were discussed.The synthesis conditions were optimized. Structures of the products were characterized by IR, 1HNMR and 13CNMR.The results showed that solvent of ethanol was appropriate, the better reaction temperature was 60-65℃, reaction time was 72-78h and molar ratio of DAM to bromoalkane was 1:1.1,the product yields were 80.05%,78.52%, 76.90% and 62.82% for diallylmethylalkyl(C12，C14，C16，C18) ammonium bromide,respectivly,under the optimum synthetic conditions. The obtained products have expected structures and good solubility in polar solvents. The present work would be the foundation for further researche on preparation and the relationship between structure and properties of the corresponding polymers.