Abstract: The seismic reflections of T₂-T₆ in the depocenter of the Yingge Sea Basin are of thick argillite sequences with rich organism. Since the organic matters in the sequences have been buried at depth over 3250m, i. e the oil/gas generating threshold,they are already transformed into hydrocarbon and the oil/gas accumulation occurred under the high pressure/high temperature in the argillite sequences. Because of the coarse grained-granules deposited at the margin of the basin and their downslidings along the basement towards the depocenter, it brought about lateral compression. Consequently, the thick argillite sequences in the depocenter upwarped along the vertical fractures and faults and the mudlump diapirism caused the formation of mudcone structures. The trap structures developed in the sequences of T₂-T₆ reflections at the both flanks of the mudcone and its top part could trap the oil/gas generated from source rocks and the hydrocarbon released during the stage of mudlump upwarping, being formed into oil/gas pools.