Abstract: Through the analysis of the casting thin sections,scanning electron microscopy(sem),high-pressure mercury injection and constant velocity mercury injection,visualized water and oil displacement experiment data,combined with production performance data,the influences on waterflood development on Niujuanhu block of Santanghu basin,such as reservoir petrology characteristic differences,the difference of diagenesis,pore types and its connected degree,the relationship between the pore configuration,pore throat ratio,microfracture reservoir microscopic factors has been carried out.The results show that the 3 blocks in the study area are of single pore type,with big pores and big throat types difference.The throat difference between blocks is the main reason for large difference of water injection effect.