The invention discloses a transient stability evaluation method for Bayesian optimization LightGBM. The method comprises the following steps: obtaining a transient stability data set of a power system; training the Bayesian optimized LightGBM by using the data in the transient stability data set to obtain an optimal parameter of the LightGBM, and then obtaining the trained LightGBM; obtaining thedata used for evaluating the transient stability of the power system on line after the power system has a fault, preprocessing the obtained data, and inputting the preprocessed data into the trained LightGBM to obtain a power system transient stability evaluation result after the power system has the fault. According to the method, the transient stability state under multiple complex uncertain factor 'combinatorial number explosion' can be quickly and accurately evaluated, and the online evaluation of the transient stability of the power system is facilitated.