The invention provides a method for controlling the water volume regulation lower limit value of nozzles in a secondary cooling loop of a continuous casting machine. The method comprises the steps as follows: (1) a flow switch valve is added in the secondary cooling loop, provided with a flow regulating valve, of the continuous casting machine; (2) according to the current real-time secondary cooling loop water volume aim set value Qaim, the magnitude relationship between the secondary cooling loop water volume aim set value Qaim and the sum of the optimal regulation lower limit values Qoptimalmin of all the nozzles in the secondary cooling loop is judged, when Qaim is smaller than the product of N and Qoptimalmin, the flow of the flow regulating valve is controlled as per N*Qoptimalmin/delta, and the flow switch valve is opened and closed alternately. With the method, the phenomena of relatively larger deviations of the atomization effect and the coverage of the nozzles when the aim-set-value water volume of the secondary cooling loop of the continuous casting machine is lower than the sum of the optimal regulation range lower limit values of all the nozzles in the loop are avoided, so that the cooling effect of secondary cooling under the condition of the relatively low secondary cooling water volume is guaranteed, and the casting blank quality is improved.