Objective: Offshore wind turbines (OWTs) are supported by driven open-ended steel piles. At present, monopiles are the most common type of foundation adopted for OWTs because of the simplicity of their design, fabrication, and installation. Compared with the piles used in offshore platforms, monopiles are shorter but heavier. Due to these characteristics, pile drivability analysis needs to be conducted to evaluate whether pile running will occur during pile driving. Methods: Based on the measured data from monopiles of offshore wind farms on site, the influencing factors of pile running are investigated, and the identification methods for pile running are analyzed. This study found that pile running easily occurs when monopiles penetrate areas where sand overlies clay. The thicknesses of the overlying sand layer and underlying clay layer will have an impact on whether pile running occurs. Results: In this study, when the thickness of the sand layer is 0.1D-0.2D (where D is the pile diameter) and the thickness of the clay layer exceeds 0.4D, the risk of pile running is the highest. When pile running occurs, because of the sudden change in bearing capacity, the penetration velocity in the pile running stage will first increase, then gradually decrease, and eventually return to 0. Therefore, the change in penetration velocity can fully demonstrate the process of pile running, and the length of the pile running can be judged based on this. A process for calculating the penetration velocity of the pile during pile driving has been proposed. Based on the process of calculating the penetration velocity, the penetration velocity was calculated. When calculating the penetration velocity during pile driving, the dynamic effect needs to be considered. The method based on the two-dimensional dynamic cavity expansion model was used to calculate the dynamic resistance. The shape parameter N required for calculating the dynamic resistance was obtained using the measured data from 27 monopiles on 3 sites. For a monopile with a diameter of 6.5-9.0 m, the shape parameter N=1.2 is appropriate. Conclusions: A method to determine the length of the pile running, which considers the static and dynamic resistance simultaneously, has been presented. The measurement results on site show that the pile running length obtained by the velocity discrimination method is consistent with that in practice. The identification method for pile running proposed in this study provides a reference for the identification of pile running of similar OWT monopiles in the future.