The embodiment of the present invention provides a baseband resource distribution method and system, and a controller, and relates to the communication technology field. The problem is solved that the whole utilization rate of the baseband source in the source pool is low in the prior art. The method comprises: the controller obtains the source overload early warning message reported by a first BBU through a switch; the controller requires source occupancy rate reported by other BBUs except the first BBU in the source pool through the switch according to the source overload early warning message; and the controller determines a target BBU according to the source occupancy rate reported by other BBUs and switches the RRU on the first BBU to the target BBU through the switch. The controller is connected with the switch, the first group of the interfaces of the switch is connected with a plurality of baseband processing units (BBU), and the second group of the interfaces of the switch is connected with a plurality of remote radio units. The baseband resource distribution method and system, and the controller are applied to the distribution of the baseband source.