The invention relates to a structure and method for solving the ice blockage problem of an expansion main refrigerating machine evaporator. The structure mainly comprises an evaporator body. End flanges are arranged at the two ends of the evaporator body. One of the end flanges is provided with a screwed plug installation opening. The evaporator body is provided with a carbon dioxide gas inlet pipe which communicates with a condenser pipe bundle inside the evaporator body. The condenser pipe bundle communicates with a carbon dioxide liquid return pipe. A gas-liquid partition plate is arranged inside the evaporator body. The evaporator body is further provided with a gas inlet connector. The gas inlet connector communicates with the condenser pipe bundle. A gas outlet valve is installed on the screwed plug installation opening, and the flange at one end of the evaporator body is provided with a sewage outlet. Compressed gas passes through the interior of the evaporator body and thaws ice deposits after entering the evaporator body from the gas inlet connector, and the ice deposits are changed into liquid water which flows out from the sewage outlet. Improvement is conducted on the basis of an existing main refrigerating machine evaporator structure so that high-pressure gas can be led into the evaporator to achieve rapid and efficient ice deposit removal.