Abstract: The tank bottom plate is one of the main risk areas of crude oil storage tanks. Addressing the difficulty of regular batch open-tank inspection for tank bottom plates, online acoustic emission testing was combined to evaluate the tank bottom plates. The results showed that the main damage modes on the upper/lower surfaces of the tank bottom plate were sediment water corrosion/soil corrosion, respectively. Online acoustic emission testing could reflect the corrosion state of the tank bottom plate without opening the tank. By introducing an acoustic emission testing correction coefficient, the failure probability of the tank bottom plate could be corrected, and the relationship between acoustic emission testing results and tank bottom plate risk could be established. Using this method, six crude oil storage tanks in an oil depot were evaluated, achieving differentiated risk assessment of tank bottom plates for tanks in the same batch. Under the premise of controllable tank risk, it was planned to open and inspect two tanks annually.