The invention discloses a building cold and heating supply system and a control method thereof. According to the system, each floor is provided with an independent sub controller and an indoor temperature sensor, and a sub water supply temperature sensor, a sub throttling valve and a sub water return temperature sensor are arranged for a heat exchanger of each floor. The sub controller immediatelycontrols valve opening degree of the sub throttling valve according to indoor temperature and set temperature at the heat exchanger of each floor, and the difference between water supply temperaturein a sub water supply pipe and water return temperature in a sub water return pipe, so that control efficiency is effectively improved, energy is saved, and the problems that in the prior art, the building cold and heating supply can not be automatically monitored and operated, and resource waste is easily caused are solved.