A control method for frequency regulation, wherein the control method is applied to a heat pump unit, the heat pump unit comprises at least a compressor and a water tank, and the control method for frequency regulation comprises the following steps: obtaining a first heat pump outlet water temperature and a first water tank temperature, wherein the first heat pump outlet water temperature is used to represent a temperature of hot water produced by the heat pump unit, and the first water tank temperature is used to represent a temperature of water in the water tank after heat exchange with the hot water produced by the heat pump unit; calculating a temperature difference between the first heat pump outlet water temperature and the first water tank temperature if the first heat pump outlet water temperature is greater than or equal to a first preset value in a first preset time period; controlling, if the temperature difference is greater than or equal to a first threshold, the compressor to perform a frequency limiting operation, and obtaining a second heat pump outlet water temperature, wherein the second heat pump outlet water temperature is used to represent a temperature of hot water produced by the heat pump unit after the frequency limiting operation; and controlling the compressor to stop the frequency limiting operation if the second heat pump outlet water temperature meets a first preset condition characterized in that the first preset value is used to represent a temperature difference between a maximum heat pump outlet water temperature and a first preset parameter and the controlling, if the temperature difference is greater than or equal to a first threshold, the compressor to perform a frequency limiting operation, and obtaining a second heat pump outlet water temperature comprises: controlling, if the temperature difference is greater than or equal to the first threshold, the compressor to perform a frequency fixing operation, and obtaining the second heat pump outlet water temperature; or controlling, if the temperature difference is greater than or equal to a second threshold, the compressor to perform a frequency reduction operation, and obtaining the second heat pump outlet water temperature, wherein the second threshold is greater than the first threshold. obtaining a first heat pump outlet water temperature and a first water tank temperature, wherein the first heat pump outlet water temperature is used to represent a temperature of hot water produced by the heat pump unit, and the first water tank temperature is used to represent a temperature of water in the water tank after heat exchange with the hot water produced by the heat pump unit; calculating a temperature difference between the first heat pump outlet water temperature and the first water tank temperature if the first heat pump outlet water temperature is greater than or equal to a first preset value in a first preset time period; controlling, if the temperature difference is greater than or equal to a first threshold, the compressor to perform a frequency limiting operation, and obtaining a second heat pump outlet water temperature, wherein the second heat pump outlet water temperature is used to represent a temperature of hot water produced by the heat pump unit after the frequency limiting operation; and controlling the compressor to stop the frequency limiting operation if the second heat pump outlet water temperature meets a first preset condition characterized in that the first preset value is used to represent a temperature difference between a maximum heat pump outlet water temperature and a first preset parameter and the controlling, if the temperature difference is greater than or equal to a first threshold, the compressor to perform a frequency limiting operation, and obtaining a second heat pump outlet water temperature comprises: controlling, if the temperature difference is greater than or equal to the first threshold, the compressor to perform a frequency fixing operation, and obtaining the second heat pump outlet water temperature; or controlling, if the temperature difference is greater than or equal to a second threshold, the compressor to perform a frequency reduction operation, and obtaining the second heat pump outlet water temperature, wherein the second threshold is greater than the first threshold. controlling, if the temperature difference is greater than or equal to the first threshold, the compressor to perform a frequency fixing operation, and obtaining the second heat pump outlet water temperature; or controlling, if the temperature difference is greater than or equal to a second threshold, the compressor to perform a frequency reduction operation, and obtaining the second heat pump outlet water temperature, wherein the second threshold is greater than the first threshold.