The offshore wind energy is increasing rapidly due to higher stability and efficiency than onshore one. However, offshore wind farms suffer from typhoon activities, which cause unpredictable outages and threaten the system secure operation. Previously, few studies consider the operating risk of offshore wind farm under typhoon conditions. To bridge this gap, this paper assesses the risk of offshore wind farm outages facing typhoon disasters. First, based on a data-driven method, typhoon tracks are simulated using empirical formulas considering uncertainties. Then the typhoon influence on offshore wind farms is analyzed to obtain the dynamic power generation. Finally, the dispatchable region is enveloped to identify power system risk states. On this basis, the resilience indices are calculated for the system secure operation. Numerical experiments are carried out to validate the proposed models and methods. The simulation results show that the operation risks of the power system can be effectively assessed under typhoon conditions.