The invention discloses a high-yield high-purity DAST source powder synthetic process. The synthetic process comprises the following two steps: 1, reacting 4-methylpyridine with methyl p-toluenesulfonate in the presence of absolute ethyl alcohol serving as a solvent to obtain an absolute ethyl alcohol solution of 4-methyl-N-methylpyridine tosilate; and 2, reacting 4-methyl-N-methylpyridine tosilate with p-dimethylaminobenzaldehyde in the presence of absolute ethyl alcohol serving as a solvent and under the catalytic action of di-n-butylamine or piperidine, so as to obtain high-yield (85-95%) high-quality (90-95%) DAST source powder. According to the synthetic process, absolute ethyl alcohol is used as a reaction solvent, harm of poisonous and harmful solvents such as methylbenzene and methyl alcohol to the body of an operator can be avoided and the pollution of waste liquid to the environment can be avoided. The research success of the high-yield high-purity DAST source powder synthetic process is beneficial to culture of high-quality large-sized DAST crystal, thereby laying a good material and theoretical basis for research on the DAST crystal and related products.