Abstract: GPS observations are influenced by external factors, resulting in various types of noise in their time series. It is necessary to use appropriate noise model to estimate the station’s velocity accuracy. Spectral analysis method and maximum likelihood estimation method are used to perform optimal noise model analysis on the time series of 259 GPS continuous stations in the China Continental Crustal Movement Observation Network. Three consecutive days of observation data are extracted from the annual continuous station data as simulated campaign stations. The main noise models of the continuous stations of China Crustal Movement Observation Network of China are white noise plus flicker noise resulted from spectral analysis method. The difference in velocity calculated using the optimal noise model and the FOGMEx model is not significant, and the speed uncertainty is 1.5 ± 0.7 times (E), 1.0 ± 0.5 times (N), and 1.8 ± 1.1 times (U) of the FOGMEx model, respectively. For the simulated campaign station, the velocity uncertainty obtained from the original continuous station covariance matrix is 0.8 ± 0.2 times (E), 1.0 ± 0.2 times (N), and 0.9 ± 0.2 times (U), respectively, compared with the velocity uncertainty estimated by the noise model established by reducing its degree of freedom and there is no significant difference in velocity. Therefore, for the majority of real campaign stations in China’s mainland, reducing the degrees of freedom (i.e., assuming the number of observed values at campaign stations equals the number of years of observation) is suggested to estimate their uncertainty.