The stability of the borehole wall is an important condition for the smooth drilling of the borehole. Reasonable wall protection technology can effectively keep the stability of hole wall， especially in the process of complex formation drilling. It is necessary to adopt suitable wall protection technology to keep the stability of hole wall to achieve the purpose of smooth drilling. During the Xiangnan No.1 Deep Drilling， the strata in several hole sections were extremely broken，and serious hole wall instability occurred. After analyzing the stratum and on-site construction technology， a set of systematic wall protection schemes were formed for different hole sections. Through the comparison of the actual wall protection effect on site，it is found that the flushing fluid is suitable for the wall protection under the condition of slight leakage， the follow-pipe drilling process is suitable for quickly passing through the local extremely broken formation， and the cement ball mixed with the cement slurry has a good effect on the protection wall of the extremely broken formation. Different retaining wall technologies have their own advantages and disadvantages. In the actual drilling process，the targeted selection of high-efficiency retaining wall technologies is of great significance to improve drilling efficiency.