The Himalayan Cenozoic leucogranites, a typical example of S-type leucogranites worldwide, are distributed mainly within two parallel W-S-trending structure belts, i.e. Tethyan Himalayan belt and the Higher Himalayan belt. Experimental results and theoretical calculations indicate that these leucogranites were derived from different partial melting of middle-lower crustal material, closely coupled with structural deformation. (1) During the period of 46~35 Ma and under the condition of thickening of the crust, the partial melting occurred mainly in amphibolite, forming granites with high Sr/Y ratio. (2) During the period of 28~9 Ma, rapid exhumation of deep crustal rocks resulted in the dehydration melting of muscovite, giving a rise to granites with high Rb/Sr ratios. (3) During the period of 21~16 Ma, fluxed melting of muscovite in the metapelites related to E—W extension along the southern Tibet rift zone, producing the granites with low Rb/Sr ratios and high Sr and Ba contents. (4) During the period of 25~27 Ma, partial melting of metapelites occurred in some areas at the high pressure.