Abstract: According to the newest re search result of global underground fluid network, using the geophysical sounding data and hightemperature and high-pressure geochemistry experiment results, we have re searched the mechanism and main characteristics of the fluid pathway in lithosphereat northernedg e of west Qinling. Ourresults indica te that there is fluid pathway th roughout the lithosphere in our re searching district with obvious characteristics. Twomain factors have played vital role in the forming process: the diapering of the fluid in the astheno sphere and the structure movement. The fluid in the pathway has acted very important operation in heat conducting and this caused a series of com plica tegeo chemistry reaction and material redistribution. The main aspect is: ①dehydration of the rocks in middle-lower crust; ② partial melting of rocks; ③ differentdensity rocks differentiate eachother, lowdensity material move upward and forming the high velocity and high conductivity layer in middle crust, highdensity material mov ing dow nward and forming the high velocity layer in the bottom of low crust.

Key words: Global fluid networks, Dehydration of rock, Partial melting of rock, Gravity differentiation