Reservoir with high porosity still developed at the second member of Yingcheng Formation in Yingtai faulted depression when sedimentary pyroclastic rocks buried underground deeper than 3 000 m. Relationships of reservoir space composition with lithology，buried depth and structural position were analyzed in order to determine reservoir characteristics and its influential factors，and the control factors of reservoir were studied from two aspects：diagenesis and the formation of high porosity zone. The results show that reservoir space of sedimentary pyroclastic reservoir in the second member of Yingcheng Formation in Yingtai faulted depression is composed of primary porosity such as intergranular pore and intraparticle pore，secondary porosity such as dissolution pore and intercrystal pore and fracture. There are three zones with high porosity：interlayers at 2 000-2 100，2 500-2 550 and 3 300-3 700 m. Reservoir is controlled by deep compaction，filling，metasomatism，corrosion-dissolution and recrystallization. The main factors about improvement of deeply buried sedimentary pyroclastic reservoir are corrosion-dissolution and matrix recrystallization. The plane porosity can increases 0.6%-5.3% through corrosion-dissolution of unstable plagioclase in this area，and the plane porosity can increases 0.9%-8.3% through recrystallization of unstable matrix. The sedimentary pyroclastic rocks have high content of unstable ingredients，which can provide material for diagenesis. So dissolved and recrystallized sedimentary pyroclastic rocks in uplift area with buried depth less than 3 700 m should be paid more attention by the exploration.