Abstract: The present paper focuses on the analysis and processing of the observational data by using the highprecision processing software gamit/globk, and the contrast of the effects of broadcast ephemeris and precise ephemeris on the LC phase residuals of GPS monitoring stations. Under the same conditions, the orbital errors by using the broadcast ephemeris tend to be 1.5 to 27.2 mm greater than those by using the precise ephemeris. These differences have something to do with the number and length of the short baselines in the stations. Through the data processing by using the dual-frequency differential analysis, for the baselines with the length of 300 km or less, the baseline errors generally range between 5 and 8 mm as using the broadcast ephemeris while the baseline errors vary from 3.2 to 6.8 mm as using the precise ephemeris; the differences of the baseline errors range between 1.2 and 1.8 mm. It can be seen from the algorithm case study in the text that both the broadcast ephemeris and precise ephemeris are well solvable when the baselines lengths come up to 300 km or less, which have increased by a big margin than the baseline length of 100 km proposed by the previous research workers. The authors in this study owe all the progress to the application of the high-precision software gamit/globk and initial coordinates, suitable constracts, effective use of the observational data and processing models.