Accurate estimation of the modern building deformation is very important for the construction safety.In order to solve high const problem of deformation monitoring of large project with global position system（GPS）

Multi-antenna technology is proposed to facilitate multi-objects monitoring with only one receiver.And the improved grey GM（1

1） model is used to analyze the deformation condition

and the tendency is predicted.It is concluded that the system can minimize costs of deformation monitoring with high measurement precision

and the improved grey model has a better precision in prediction.