The invention relates to a ground clutter interference real-time suppression method for a space-based external radiation source radar. The ground clutter interference real-time suppression method comprises the steps of: completing key parameter design of a space-based external radiation source radar system according to transmitting and receiving time sequence requirements for system RF signals; analyzing spatial position and moving relation between a space-based radar platform and an external radiation source, and establishing a space-based external radiation source radar ground clutter mathematical model; constructing a reference signal by utilizing a direct wave signal, carrying out cross-correlation processing on the reference signal and a target signal received by a two-channel echo antenna; eliminating ground clutter interference of correlation result of an nth frame signal of a channel 1 and correlation result of an (n-1)th frame signal of a channel 2 by adopting a two-pulse canceller; and repeating the cross-correlation processing and the two-pulse cancelling steps for carrying out Fourier transform on N frame signals after clutter suppression along a speed dimension to achieve phase-coherent accumulation, and adopting a constant false-alarm criterion to realize target detection. The ground clutter interference real-time suppression method can be used for suppressing clutter interference effectively, reduces complexity of the algorithm, and is convenient to achieve real-time data processing of the space-based platform.