The deeply-buried Tertiary clastic reservoirs of the Well Kun 2 in the Qaidam basin are mainly composed of lithic sandstones and feldspathic lithic sandstones with lower compositional and textural maturation degrees. The much higher content of matrix (generally >15%) is the dominant cause for porosity damage during sedimentation of these clastic reservoirs. The reservoirs in Well Kun 2 have undergone the mechanical compaction, cementation, replacement, and weak dissolution, of which the compaction and carbonate cementation with different phases are the two main factors responsible for porosity reduction during the increasingly progressive diagenesis. The deeply\|buried reservoirs (including N₁, E₃ and E₁₊₂) are now in late B period of early diagenetic stage, and periods A and B of late diagenetic stage. The diagenesis occurred in the alkline diagenetic environment controls the diagenetic evolutionary features of deeply\|buried clastic reservoirs in Well Kun 2. The clastic reservoirs distributed in Upper Ganchagou Fm.(N₁) are mainly low porosity-low permeability sandstones containing a few extremely low porosity and permeability reservoirs, with porosity ranging from 0.1 to 15.59%, averaging 7.75%, and permeability from 0.1 to 37.38×10^-3μm², averaging 13.23×10^-3μm². The reservoir spaces of the clastic reservoirs are mainly compressed intergranular pores which are favorable for preserving natural gas, but could also contain a few crude oil. The reservoirs of Lower Ganchaigou Fm.(E₃ ) are mainly extremely lower porosity and permeability clastic sandstones, with porosity varing from 2.2%~14.3%, averaging 5.0%, permeability from 0.02 to 5.55×10^-3μm², averaging 0.58×10^-3μm², which can act as gaseous hydrocarbon reservoirs with dominant spaces composed of fracture pores.