Considering the strong non-linearity and randomness of impact load, the probability model of impact load and the excited rule by sea environment of cylindrical Floating Production Storage and Offloading (FPSO) are studied by model test method. A method based on the dimensionless model of wave surface rise is proposed, and a small amount of impact data with 1 000 a and 100 a return period are normalized and fitted to obtain the impact load characteristics of cylindrical FPSO. The results show that the motion of the platform itself is of important influence on the impact probability, and the acceleration phase of the impact probability is of no obvious relationship with the location of the impact point. With the increase of the location of impact point, the magnitude of impact load of the cylindrical FPSO tends to increase. Due to the upper overturning structure of the cylindrical FPSO, the probability of the impact stimulated by the sea state with the spectral peak period close to the heave period of the cylindrical FPSO will increase. The dimensionless impact probability model and dimensionless impact load distribution model constructed can predict the impact load and impact probability, and the model can provide a basis for long-term simulation.