The invention relates to a mixed jet generation method and a drainage structure thereof. The structure comprises an A medium flow guiding member, a B medium flow guiding member and a conflux cambered surface; the jet axis of each of the A medium flow guiding member and the B medium flow guiding member is tangent to the conflux cambered surface; and the tail end of the conflux cambered surface is provided with a jet end, the total length from the jet end to the cambered surface of the jet port of the A medium flow guiding member is l, the total length from the jet end to the cambered surface of the jet port of the B medium flow guiding member is L, and L is greater than l. The method is characterized in that the direction of jet direction of the A medium flow guiding member along the conflux cambered surface is same to the movement direction of a decontamination solution nozzle along the conflux cambered surface, the decontamination solution is driven under high speed airflow and is jetted along an optimized curve to form a thin layer water curtain or curtain-shaped water droplets, and different decontamination effects can be reached by adjusting the mixing ratio of gas and liquid in order to realize high application degree.