The present invention discloses an uplink data transmission method and device configured to shorten RTT in a transmission condition having a short time slot, thus reducing a user-plane latency and improving the system performance. An embodiment of the present invention provides an uplink data transmission method. The method comprises: determining, by the network side, a time slot size for data transmission, and sending, according to the time slot size, uplink scheduling signaling to a user equipment (UE); and receiving, by the network side and according to a predetermined scheduled timing, uplink data sent by the UE, wherein the time slot is a time unit having a duration smaller than 1 ms, and the predetermined scheduled timing is that when the network side employs a time slot n to send the uplink scheduling signaling, the network side receives the uplink data sent by the UE in a time slot (n+1), with l∈L, n and l both being integers greater than or equal to zero, and L denoting the set of selectable values of l.