Abstract: In the drilling process of Nanpu Oilfield, underground complex such as wellbore collapse, drilling bit blocking and electric logging difficulty was caused by shale flaking off in Dongying formation and Shahejie formation. Based on analysis of physical and chemical characteristics of deep shale and its collapse mechanism, inhibitive drilling fluid with strong sealing ability was proposed to be the effective measure to prevent deep shale flaking off, which is of great significance for improving ROP and reducing the occurrence of underground complex in Nanpu Oilfield.