Abstract: GPS ambiguity resolution has always been difficult for real time kinematics surveying, so it is an attractive method to combine GPS observations with the geometry information from other surveying system to improve the ambiguity resolution. In kinematics deformation surveying, the prior geometry information can be obtained from different methods, so it can be used to improve GPS ambiguity. It deals with the collection and the description of the prior geometry and the method using geometry validation to improve the ambiguity resolution. The principle of the method, the relationships between the geometry threshold and the ambiguity search space are presented. A method to determine the threshold for the geometry validation is suggested. The field tests are carried out to show the feasibility of the proposed methods.