The invention discloses a cultivation tank nutrient liquid temperature control system and a control method thereof. The control system comprises a constant temperature control device, a ventilation device, a cultivation tank and a heat insulation board. The cultivation tank is internally provided with a circulation pipe whose two ends communicate with the constant temperature control device through infusion tubes. A planting plate is arranged above the cultivation tank. The ventilation device supplies gas to a nutrient solution inside the cultivation tank through a gas transmission pipe. The temperature setting is carried out through the constant temperature control device, the circulation pipe and the nutrient solution are in full contact, and the temperature of the nutrient solution is effectively controlled and maintained. Through setting the heat insulation board, the heat insulation effect of the cultivation tank is enhanced, the temperature loss of the nutrient solution is reduced, the temperature of the nutrient solution can be controlled in a range of plus or minus one DEG C of a temperature set by the constant temperature control device, the needs of plant growth are satisfied, the utilization rate of the nutrient solution is improved, through a program control method and a single-point control method, and the temperature cycle control and direct control of the plant are achieved, which is convenient, fast and efficient.