Abstract: Aiming at the steeply dipping narrow and broken veins, the sublevel caving mining method can effectively reduce the collapsing of surrounding rock and ensure the safety of workers, which use the caving rocks to fill the mining gap.However, the extraction of ore under broken rock has brought a new problem of ore loss and dilution.This paper uses the similar physical model test to analyze the law of the granular under the inclined side wall with narrow space.The test results show that the axis of the isolated extraction zone is deflected by the inclined side wall, and the shape is varied.With the increase of the accumulated extraction ore, the shape of isolated extraction zone is “invasive” and develops along the inclined side wall.We also acquire the relationship between the width and height of the isolated extraction zone with the cumulative amount of extraction ore.According to the morphological characteristics of the isolated extraction zone, the broken rock moving area in the process of extraction under the narrow space of the inclined side wall is divided into three zones of the extraction draw point control zone (with Z< 10 cm), the transition zone (with 10 cm≤Z< 32 cm), and the inclined side wall control zone (with Z≥32 cm).According the results, the sublevel height of sublevel caving method is not good to exceed the transition zone.