Abstract: By analyzing the coefficient formula between displacement and strain,the whole solving method using multi-surface function,which can calculate strain field in large region,is proposed.The theoretical strain field and calculation strain field of simulation data are given.In this simulating process,the 1 grid data and 50% constraining data are used as simulating input.By comparing the theoretical results and calculating results,the strain calculating method is tested effectively.Meanwhile,we analyze the GPS strain field of region network in China mainland using 1999-2004 GPS velocity fields and give the strain field distribution.The characteristic of multi-surface function method is discussed,and advice of strain calculation is given.