The traditional use of the acetic acid ammonolysis method in conjunction with ordinary rectification to synthesize high-purity acetonitrile cannot directly purify acetonitrile mother liquor in the absorption process to acetonitrile product (high-purity acetonitrile must typically have ≤0.1 wt.% water content). This new process uses a new unit with rectification-pervaporation membrane coupling to perform recovery, which achieves a high recovery rates and simplifies process procedures. Other advantages include a high safety coefficient, high energy utilization rate, low feed liquid recycle volume, and low operating energy consumption.