Embodiments include a physical resource block scheduling method, network device, and system, which may be used to perform scheduling request indicator SRI scheduling. The method includes: receiving a scheduling request indicator SRI sent by user equipment UE; allocating M PRBs to the UE according to a reference quantity of bits for scheduling; receiving, on a physical uplink shared channel, an uplink transmission block TB that is sent, in response to current-time SRI scheduling, by the UE; and determining, according to the uplink TB, a reference quantity of bits for scheduling for next-time SRI scheduling of the UE.