The invention discloses an ash-clogging alarm identification system and method for an ash tank of a thermal power plant and relates to the technical field of automatic over thermal power plants. The system comprises a temperature measurement mechanism and a controller. The temperature measurement mechanism is arranged at the outer side of the ash tank and comprises multiple thermal resistors, thethermal resistors annularly wind the outer wall of the ash tank, the annular thermal resistors are evenly distributed in the vertical direction, and each thermal resistor is electrically connected with a temperature measurement instrument; the controller is electrically connected with an output end of the temperature measurement instrument and comprises a data collection module and a data analysismodule, the data collection module is used for collecting temperature data measured by the temperature measurement instrument, and the data analysis module is used for analyzing whether or not temperature difference values of the cross sections, at different heights, of the ash tank are normal and giving an alarm signal when the temperature difference values are greater than a normal temperaturedifference value. The system can monitor the temperatures of the cross sections, at different heights, of the ash tank in real time and calculate the temperature difference value between every two temperatures, by comparing the temperature difference values, whether or not ash-clogging of the ask tank occurs is judged and the ash-clogging position is judged, and an alarm is given out when ash-clogging occurs.