A method for uplink data transmission, a terminal device and a network device are provided. The method may include: receiving subset constraint indication information of an SRS resource sent by a network device, wherein the subset constraint indication information is used for indicating at least one available SRS resource subset; according to the subset constraint indication information, determining the length of an SRI, sent by the network device, in DCI for scheduling uplink data transmission; according to the length of the SRI, determining a target SRI from the DCI; determining, in the at least one available SRS resource subset, a target SRS resource subset corresponding to the target SRI; and according to the target SRS resource subset, determining a transmission parameter used for the uplink data transmission.