The invention discloses a preparation method of methyl p-methoxycinnamate. Add methyl acetate, methanol, sodium methoxide and cyclic ether into the condensation reactor, and react at reflux temperature; then add p-methoxybenzaldehyde, and circulate the reaction solution through the reaction bed filled with catalyst, After the addition of benzaldehyde is completed, the reaction is continued by reflux and insulation, and the water generated by the reaction is separated and removed. By adding methanol and cyclic ether and removing the generated water, the amount of catalyst used can be reduced to a very low level. By circulating the reaction solution through the reaction bed equipped with metal oxide catalysts, the 3 generated in the reaction process ‑Methoxy‑3‑methyl p-methoxyphenylpropionate is converted into methyl p-methoxy cinnamate in time, which improves the purity and yield of the product, and at the same time does not require acid-base neutralization process, and does not generate excess waste water and Compared with traditional processes, other solid wastes have equivalent or higher conversion rates and selectivity, lower production costs, and are more environmentally friendly.