The invention discloses a clustering-based power system transient power angle stability fault screening method and device, and the method comprises the steps: sampling historical data according to a transient power angle margin range based on the online safety analysis and application of result data stored by a transient stability evaluation function for each fault; and clustering samples with consistent transient power angle stability and stable modes and similar transient power angle margins into a plurality of historical operation mode clusters, and determining the optimal cluster number ofeach fault by using a contour coefficient method; classifying each fault of the specified operation mode, and estimating the transient power angle margin of each fault; and finally, obtaining a severe fault set composed of a transient power angle instability fault set and transient power angle stability faults of which the transient power angle estimation margin is greater than a set threshold. By adopting the method, the transient power angle stability evaluation fault set investigated by the online analysis application can be quickly screened, and the number of faults of transient power angle stability evaluation is effectively reduced, so that the calculation speed of transient safety and stability analysis is increased.