The invention discloses a charge-discharge control method and system of a redox flow battery and the redox flow battery. The method comprises the following steps of 1, detecting SOC of the redox flow battery; 2, judging whether the SOC of the redox flow battery is between an SOC lower limit and an SOC upper limit or not, if yes, executing the step 3, otherwise executing the step 4; 3, maintaining a voltage of the redox flow battery unchanged; and 4, adjusting the voltage of the redox flow battery to be lower than a first preset voltage when the SOC of the redox flow battery is larger than or equal to the SOC upper limit, and adjusting the voltage of the redox flow battery to be between the first preset voltage and a second preset voltage when the SOC of the redox flow battery is smaller than or equal to the SOC lower limit, wherein the second preset voltage is higher than the first preset voltage. By the method, the problems of side reaction is easy to generate in the redox flow battery under a high SOC condition and capacity attenuation of the redox flow battery caused by high SOC charge for a long time are prevented, and meanwhile, the upper limit of a charging voltage can be increased under a low SOC condition so as to improve charging quantity.