With GPS, VLBI, SLR and other techniques Crustal Movement Observation Network of China (CMONOC) provides a large scale network of crustal observation of high accuracy and spatial and temporal resolution. It is mainly for earthquake predication so most of the GPS observation stations are deployed along faults. In some areas the amount and distribution of GPS observation stations are not as desired. Hardy function interpolation, bi-cubic interpolation function have been used to intensify the GPS network, but the results are not so good. Finite element method and discontinuous deformation analysis are also introduced to simulate the velocity fields. Both the finite element method for continua and the discontinuous deformation analysis for block systems are special cases of numerical manifold method, which is a newly developed general numerical method based upon mathematical manifold. In numerical manifold method the cover displacement functions on individual cover are connected together to form a global displacement on the domain. In this paper Chuandian's crustal motion velocity field is simulated by numerical manifold method with GPS observations. The derived velocity field can well represent the continua and discontinuous zones of Chuandian.