The invention provides a liquid balance control method for a copper electrolysis system. A low-position collecting pool (1) and a high-position tank (2) which are connected with each other through a pipeline and a water pump (3) are arranged; the high-position tank is provided with a liquid level control valve (4), and meanwhile is provided with an overflow pipe (5) by which flow returns to the low-position collecting pool to form a closed loop for collecting water; a water outlet pipe (6) is connected to the inside of the high-position tank, and respectively communicates with water supply systems of mechanisms of electrolyte pump cooling water, belt filter sealing water, equipment flushing water, process water and field cleaning water in a copper electrolysis technology, and the used electrolyte pump cooling water, volatilized water generated by evaporation and concentration of electrolyte, condensate water generated by heating of the electrolyte and the belt filter sealing water communicate with water drainage systems of the low-position collecting pool, the equipment flushing water, the process water and the field cleaning water through pipelines by the water outlet pipe (6), so that a liquid cycle is formed. By the liquid balance control method for the copper electrolysis system, consumption of production water can be reduced, sewage treatment load is reduced, liquid balance of the electrolysis system is controlled, and volume expansion in a copper electrolysis process is avoided effectively.