The present invention provides an upstream bandwidth allocation method, apparatus, and system. The method includes: obtaining, by a cable modem termination system (CMTS), a service flow attribute of each online cable modem (CM), where the service flow attribute includes a delay-sensitive service and a delay-insensitive service; allocating, by the CMTS, an upstream bandwidth to each online CM according to a preset total bandwidth and a received service request, and obtaining a remaining bandwidth after the bandwidth is allocated according to the service request; allocating, by the CMTS, at least a part of the remaining bandwidth to each CM whose service flow attribute is a delay-sensitive service, and informing each online CM of an upstream bandwidth allocation result, so that each online CM performs upstream data transmission according to the allocated bandwidth. The remaining bandwidth after allocation is actively allocated to a CM corresponding to a delay-sensitive service, so that upstream throughputs of some CMs are increased, and upstream transmission delays are reduced.