The invention discloses a model-free transient stability situation estimation method based on data drive. The method comprises: based on the state space reconstruction theory, decomposing a transient power angle stability analysis problem of a power system into an MLE (Maximum Likelihood Estimation) trajectory analysis problem of the most seriously distributed unit on the relative power angle curve of the system; then, improving the classical MLE calculation method by using a recursive least square algorithm; further giving a parameter optimization method for the transient power angle stability problem of the power system in MLE calculation; and finally, giving a judgment basis for transient power angle stability in combination with the MLE curve of the seriously distributed unit on the system, thereby realizing online estimation of transient power angle stability situation. The method for online calculation directly using measurement information has high engineering application value.