Abstract: In analysing the data of earthquakes of magnitude M 6 occurred in Yunnan and Sichuan provinces of southwestern China since 1920, it seems that a correlative relation exists in time and locality, with a probability of 78%. At the same time, the probability of the order of migration of earthquakes from Yunnan to Sichuan and from Sichuan to Yunnan is essentially equal, the intervals between origin times are about the same as well, the direction of migration of earthquakes is predominately northeast.Statistical results show that the interval (△) between events of Yunnan and Sichuan are generally short-about 9 months in average. X2 tests indicate that they obey the Poisson Distribution. The areas with higher correlative probability are given on the basis of discussions of their respective specific features. When an earthquake event occurs in an area, then the origin time, the location and the probability of the occurrence of an event in another area may roughly be estimated, thus providing a clue for medium-range earthquake prediction.Some problems concerning the mechanism of the correlative relation of earthquakes of Yunnan and Sichuan provinces have also been discussed in this paper,