Abstract: With the depletion of shallow resources and the development of coal mining, the disaster of soft rock engineering is prominent. Based on the engineering background of II66 auxiliary descending of Liuqiao No.1 mine, according to its deformation and instability characteristics, the mechanism of auxiliary descending asymmetric deformation and failure is analyzed by means of field measurement, laboratory experiment, theoretical analysis, numerical simulation and industrial test, and the optimal control measures are proposed. The research shows that :(1) the auxiliary downhill floor is weak and broken, and the roadway has significant asymmetric deformation. The surrounding rocks are of low strength, and the fine sandstones are rich in hydrophilic minerals such as illite, feldspar and chlorite. (2) according to the in-situ stress measurement, it is found that the auxiliary down-hill is in the stress zone of the plateau rock. The maximum main stress is horizontal stress and has obvious direction, and the included Angle with the roadway axis is large, which is not conducive to the stability of the surrounding rock. (3) the original support scheme did not adopt bottom control measures, ignoring the stability of u-shaped steel bearing structure, and the failure of bottom plate drives the instability of wall; (4) the numerical analysis results are close to the field observation, and the auxiliary down-slope is greatly affected by the adjacent excavation engineering disturbance, which is the main reason for its asymmetric failure. (5) based on field observation and analysis of deformation and instability mechanism, multi-level combined control measures of grouting bolt and grouting anchor cable are adopted, and structural reinforcement of u-type support is carried out at the same time, which results in good industrial test results and meets the field requirements.