The invention discloses a thermal-power-generating-unit combustion control system performance evaluation method based on data driving. The thermal-power-generating-unit combustion control system performance evaluation method includes the following steps: A, dividing the running period of a system into a plurality of intervals, and collecting output data N and output data M of the system in two randomly-selected intervals; B, carrying out standardization processing on deviation data of the output data N and deviation data of the monitoring data M; C, respectively solving covariance matrix evaluation functions of the corresponding data obtained after the data N and the data M are standardized; D, evaluating the performance of the system according to the evaluation functions obtained in the step C; E, collecting deviation data corresponding to the output data M of the system in the other intervals, then repeating the step B, the step C and the step D, and evaluating the performance change conditions of the whole control system and variables. By means of the thermal-power-generating-unit combustion control system performance evaluation method, extra disturbance can not be generated on normal running of the system, and the performance of the multi-variable control system can be simply, reliably and accurately evaluated.