<p>In the mining process of underground metal mines, some ores have not been mined due to factors such as ore quality, technology, and economy, resulting in residual ore. Moreover, due to the long-term mining by a open-pit method, the remaining large volume goaf group is prone to caving and collapsing of the goaf, resulting in safety accidents. Fully recovering this part of residual ore resources cannot only improve the economic benefits of the mine and extend the service life of the mine, but also deal with the remaining goaf while recovering the residual ore, which can fundamentally eliminate the safety hazards of the goaf. Therefore, it is urgent to study the feasibility of non-cementation of waste tailings in residual mine recovery. In order to study the effect of unconsolidated filling of waste tailings, the sliding instability evolution process of unconsolidated filling of waste tailings in the process of residual ore recovery was studied from the microscopical perspective. An experimental device for the bearing characteristics of the waste rock-tailings mixed backfill was developed to carry out uniaxial compression test. The evolution process of the failure of the waste rock-tailings unconsolidated backfill was analyzed and studied by using the load pressure yield and stress changes of the sample, and the simulation parameters were calibrated. PFC3D was used to simulate and explore the stress change and granular evolution process during the loading process. The research results show that with the increase of waste rock content, the bearing capacity of waste rock tailings filling gradually increases. When mining adjacent residual ore, the higher the mining face height and the lower the opening position, the greater the impact on the goaf filling body and the more unstable the filling body will be. The results have guiding significance for the goaf filling and residual ore mining.</p>