Abstract: In order to meet the requirement of quick responsibility and non-constraint in rea-l time collaborative editing systems,in this paper,we propose a novel responsive fine-grain optimistic locking concurrency controlling algorithm based on relative position for consistency maintenance in rea-l time distributed collaborative systems.In this algorithm,reading lock and editing lock are taken into account. The starting position of locking region and the position of editing operation are expressed in relative values,and they are not transformed into absolute positions until operations are sent to cooperative sites or locks are added into the Lock Table.Additionally,the locking granularity can be selected by editors optionally,and any coeditor can edit in advance before his／her requested lock is confirmed.This algorithm has been used in our collaborative editing system,and the experiments show that the concurrency controlling algorithm can well ensure the data consistency and quick responsibility.