Abstract:    According to the fact that there is no enough research of the extra long-baseline in GPS data processing with high precision. Focusing on the data of two CORS networks with different given points and dividing the processing time into the following six time periods: 4 hours, 6 hours, 8 hours,12 hours, 18 hours, this paper quantitatively analyzes the effects of different given points and extra long-baseline on GPS data processing with high precision. The result shows that extra long-baseline can make an effect on the accuracy of GPS data processing: the effect gets less as the increase of the processing time. And it also shows that the existence of the extra long-baseline has a relatively great effect on the result: when the given points locate worse, the maximum effect can reach 12.7mm, and when they locate better, the maximum effect gets to 6mm, and the effect is obvious in all of the 6 time periods. So the effect of extra long-baseline should be taken into consideration in GPS data processing with high precision.