The invention discloses a flow corrosion leakage detection and risk assessment control method for a reaction effluent air cooler. employing a hydrogenation air-cooling tube bundle device to enable upper and lower rows of tube bundle structures to be installed between an inlet tube box and an outlet tube box in a parallel manner, wherein each tube bundle is communicated with the inlet and outlet tube boxes, and each tube bundle structure is provided with four pressure sensors; injecting a multi-phase flow medium from the inlet tube box during operation, and finally enabling the multi-phase flow medium to flow out from the outlet tube box; recording a pressure calibration value of a pressure sensor during no leakage; taking the mean value of pressure calibration values of four pressure sensors of the same tube bundle structure as the pressure geometric mean value during operation, calculating and obtaining a pressure difference value according to the two values, judging whether there is a leakage risk or not and the level of the risk through the pressure difference value, and blocking the connection channels, connected between the inlet and outlet tube boxes, of the tube bundles if there is the leakage. The method can effectively detect the pressure condition of a cross section of a tube bundle, carries out the evaluation of the leakage degree and the risk level, effectively reduces the flow corrosion leakage risks, and prevents a safety accident.