On the basis of the data of Crustal Movement Observation Network of China(CMONOC), the characteristics of baseline length and direction
changes before and after Kunlun Mountain earthquake are studied.According to the rupture direction of Kunlun Mountains earthquake and the characteristic difference in the different bearing of baseline change,the sensibility problem that related change of baseline length and direction to the earthquake are discussed theoretically. The study shows that: 1) If the baseline direction is consistent with the earthquake’s fracture direction then the sensibility of baseline length will be higher than baseline direction; 2)If the baseline direction is vertical to the earthquake’s fracture direction then the sensibility of baseline direction is higher than baseline length; 3)If the baseline direction makes angle 45° to the earthquake’s fracture direction then both the baseline length and baseline direction may evidently change before the earthquake.