A method for time synchronization in a distributed control system includes the steps of: when a sync is received from a master-side, confirming both a reception time point of the corresponding sync and a compensation time point of a previous frequency, and determining if a result obtained by confirming the two time points corresponds to a preset Frequency Compensation Interval (FCI); performing only a time offset compensation operation when the result obtained by confirming the two time points does not correspond to the preset FCI; and performing both time offset and frequency compensation operations when the result obtained by confirming the two time points corresponds to the preset FCI.