Abstract: in the paper,the scientific thinking and principles for establishing the GPS crustal deformation monitoring network in the region of the Capital Circle and the basic conditions of the network and the major technical measures adopted to improve the observation accuracy are described systematically.This network is a GPS monitoring network with the largest scale and highest accuracy in China. The establishment and measurement of the network have already been accomplished at present,and the expected accuracy will be better than 5×10-8.This network can play an important role in earthquake monitoring and predicting.