The ore-forming metallogenic specialization of felsic rocks is closely related to oxygen fugacity. In this paper, however, oxygen fugacity is considered to be one of the necessary but not sufficient conditions for ore formation, and the analytical thinking concerned is partly based on the authors' geological field work. The metallogenic significance of oxygen fugacity is divided into metallogenic specialization and ore-bearing potential. Two aspects of understanding have been otained: ① Porphyry Cu-Au deposits derived from the reduced I-type granitoid should have a high oxygen-fugacity origin; different sub-regions within the covariogram of oxygen fugacity versus other geochemical parameters, such as degree of magmatic evolution, temperature, pressure, pH, sulfur fugacity and rock-type, correspond to different metals' geochemical behavior or mineralization, respectively, and oxygen fugacity versus rock-type seems to be of significant specialization; ② The evolution from metallogenic specialization to real metallogenesis is the evolution from magma to hydrothermal solution and then from hydrothermal solution to ore; during such a process, oxygen fugacity is also an essential controlling factor for elemental geochemical behaviors, whose influence on mineral precipitation, however, should not be overemphasized, because some kinds of precipitation might have had nothing to do with oxygen fugacity.