Abstract: The timing failure of basic roof of large mining height stope in steeply dipping coal seam results in the sequential pressure of the working face, the bearing state of supports in different regions is dissimilar, and the difficulty of surrounding rock control and production risk increase. In order to find out the failure mechanism of the sequential failure of the basic roof, the temporal failure characteristics of the basic roof, bearing structures in different regions of the working face, and the periodic collapse length of the basic roof were studied by field measurement and theoretical analysis. The results show that the timing failure characteristics of the basic roof of the high-inclination working face are the first middle part, the second upper part, the next lower part, and the broken rock mass (gangue) asymmetrically filling the goaf, which results in the different mechanical performance of gangue to overburden in different areas of the working face, forming a partitioned mechanical bearing structure; the basic roof is in the mechanical environment of different strength, and the action of different strength force leads to different falling step distance of the basic roof, thus causing the timing failure.