The invention relates to the field of power generation, and discloses a prejudging device and method for operating risks of a generator set. The prejudging device comprises an input module, a control logic synchronization module, a real-time working condition synchronization module and a processing module, wherein the input module is used for inputting operating instructions into the processing module; the control logic synchronization module is used for synchronizing control logic in the processing module with control logic in a distributed control system of the generator set; the real-time working condition synchronization module is used for synchronizing generator set working condition data in the processing module with generator set real-time working condition data in the distributed control system; and the processing module is used for simulating operation of the generator set so as to obtain simulation operating results based on the operating instructions, the synchronized control logic and the synchronized generator set real-time working condition data, and matching the simulation operating results with preset operating risks so as to determine whether the operating risks exist or not. By adoption of the prejudging device and method for the operating risks of the generator set, the operating risks of the generator set can be prejudged, a decision-making basis can be provided for significant operation of the generator set accordingly, and the safety and stability of operation of the generator set are improved.