The invention discloses a switch service flow capacity controlling method. The invention comprises that a real time value of a total flow capacity of a switch outlet service flow is monitored; whetherthe total flow capacity of the service flow is congested or not is judged according to the real time value of the total flow capacity; a flow capacity speed limiting value of the switch inlet serviceflow is adjusted according to a weighting ratio of the service flow and the judging results, which realizes the flow capacity control of the service flow. The invention also discloses a switch service flow capacity controlling device. With the invention, when the service flow with a high priority has a lower flow capacity, the flow capacity speed limiting value of each switch inlet service flow is adjusted dynamically, and the remained bandwidth of the high priority service flow is used to provide extra bandwidth for other service flow, which effectively utilizes the bandwidth resources inside the switch. And due to the limitation of the flow capacity of each service flow at the inlet, a forwarding channel during a cross-chip retransmission and the backplane bandwidth during a cross-service retransmission are saved.