Disclosed are a method and an apparatus for uplink transmission in a communication system. An operation method of a terminal includes: receiving, from a base station, first SFI information indicating n flexible symbol(s); receiving, from the base station, second SFI information re-indicating m symbol(s) of the n flexible symbol(s) as uplink (UL) symbol(s); and transmitting an SRS to the base station through the m symbol(s) re-indicated as a UL symbol among the n flexible symbol(s) indicated as a flexible symbol. Therefore, performance of the communication system can be improved.