A preheating control system of an information processing device and a control method thereof are described. The system includes a temperature sensing module, a first controller, a heating module, and a second controller. After receiving a power ON signal, the first controller shifts to a primary control mode and determines whether temperature of the hard disk satisfies an operating temperature scope or not. When the temperature does not satisfy the operating temperature scope, the heating module is used to heat the hard disk. When the temperature satisfies the operating temperature scope, the first controller shifts to a secondary control mode and activates the second controller to execute a boot program of the information processing device, thereby improving system stability.