In this paper, the author introduces the basic principle of mineral spatial distribution in migmatites, i. e. minerals in leucosomes which have reached the magmatic stage are spatially characterized by random distribution, whereas those in leucosomes from solid materials exhibit aggregate distribution; besides, he presents two statistical methods, namely contact-frequency method and line-transection method. A study of mineral spatial distribution in migmatites suggests that there exist defects and limitations in the statistical method Put forth by previous workers. The author has deduced the equation for calculating probabilities of mineral contact types and also defined the extreme dispersion degree as the Probabilities of mineral contact types in the extremely dispersed state of minerals within a rock. Minerals show aggregate distribution in a few leucosomes, but are characterized by dispersed distribution in the overwhelming majority of leucosomes. The evidence obtained from mass balance calculation,geochemical studies and mineral thermobarometer reveals that the genetic mechanism of the migmatitic complex with thermal centers is anatexis and matasomatism, with the genetic model being "the early stage metasomatism induced by thermal anomalies, the main stage anatexis induced by the early stage metasomatism, and the last stage post-anatexis metasomatism".