The invention discloses a method for synthesizing a chemical intermediate, in particular to a method for preparing 3-methoxy propylamine by taking 3-methoxy propanol as a raw material. The method takes the 3-methoxy propanol as the raw material and takes Cu-Co/Al2O3-diatomite as a catalyst. At certain pressure and certain temperature, the 3-methoxy propanol is driven into a preheater and is mixed with ammonia gas and hydrogen; the mixture is preheated and vaporized and enters a fixed-bed reactor for reaction, the material after reaction is subjected to condensation and cooling, the gas and the liquid are separated, the 3-methoxy propylamine as the product is produced, and the system materials can be recycled. The method has the advantages of simple technique process, high rate of conversion, good selectivity, a few side products, simple and concise separating flow, low energy and raw material consumption and low production cost of the product.