The invention relates to a hydraulic oil cooling system, a control method and a crane. The hydraulic oil cooling system is arranged in a hydraulic system comprising two or more sub-systems executing different operations and comprises a starting temperature control switch, a stopping temperature control switch and a controller, wherein the starting temperature control switch is used for outputting signals when the temperature of an oil return path rises to T1; the stopping temperature control switch is used for outputting signals when the temperature of the oil return path falls to T2, and T2 is smaller than T1; the controller is used for controlling a heat radiator to carry out heat radiation at heat radiation power adaptive to the sub-system working currently after receiving the signals output by the starting temperature control switch and controlling the heat radiator to stop working after receiving the signals output by the stopping temperature control switch. According to the hydraulic oil cooling system and the control method, different heat radiation power gears can be selected for the different sub-systems, real-time detection is carried out in combination with the starting temperature control switch and the stopping temperature control switch, the situation that a heat radiation system starts and stops occasionally due to the fact that the heating amounts of all the hydraulic sub-systems are inconsistent can be effectively avoided, and therefore the reliability of the heat radiation system is improved, and the service life of the heat radiation system is prolonged.