Abstract: On the basis of the GPS single epoch solution algorithm in attitude determination application,another GPS single epoch solution algorithm using the max deformation size and deformation characters constraints combined with Cholesky decomposition method in deformation monitoring application is developed.The ambiguity search space is set up directly in this arithmetic and it will become very small if there is only horizontal or vertical deformation.From the GPS test,it shows that the methods is very efficient,and the success rate is also improved expansively.