Multiple on-line system and mode control method and device thereof

The invention discloses a mode control method of a multiple on-line system. The method comprises the following steps that the indoor environment temperature is detected in real time, and a temperature difference value is calculated according to the indoor environment temperature and the temperature set by a user; an operation mode of the multiple on-line system is acquired according to the temperature difference value, and the multiple on-line system is controlled to operate in the acquired operation mode for the first preset time; a current mode of the multiple on-line system is judged; the multiple on-line system is controlled to perform mode switching according to the current mode of the multiple on-line system and a current temperature difference value. According to the control method, not only can the automatic mode demand of the user be met, but also the normal operation demand of the system can be met, and the user experience is enhanced. The invention further discloses a control device of the multiple on-line system and the multiple on-line system.