Abstract: As a low-cost technology for large-scale harmless disposal of solid waste, gangue slurry backfilling in goafs is an important solution to the challenge of solid waste accumulation in mining areas. However, the industrial application of this technology has been severely hindered by two interrelated issues: the fundamental mechanisms governing the injection of gangue slurry into complex goaf environments remain poorly understood, and the engineering adaptability of slurry injection in different underground spatial zones remains insufficient. Focusing on the entire process of surface fluidized backfilling of coal gangue, this paper systematically reviews the research progress in key aspects, including void space quantification, slurry rheological properties, long-distance transport stability, and environmental safety control. On this basis, a complete technical framework is established, encompassing five key stages: goaf void quantification, slurry preparation, pipeline transport, borehole injection, and risk prevention and control. From a theoretical perspective, this study systematically investigates overburden failure behavior and the resulting evolution of void space in response to goaf backfilling. First, a zonal injectability evaluation model is proposed to provide a precise quantitative characterization of the effective backfillable volume, moving beyond qualitative assessments. Second, the study reveals the complex transport and deposition mechanisms of high-concentration coal gangue slurry, treating it explicitly as a non-Newtonian fluid. The analysis focuses on elucidating its diffusion patterns and the subsequent accumulation and packing behavior within the porous medium of the fractured goaf. From the perspective of equipment and process optimization, key technological breakthroughs have been achieved through the development of an integrated intelligent control platform, a modular slurry preparation system, and a real-time pipeline monitoring system based on distributed acoustic sensing (DAS) technology. These advances effectively address the long-standing challenges of ensuring safe long-distance transport and providing reliable blockage warning for gangue slurry under complex operating conditions. Regarding environmental impacts, this study establishes a comprehensive evaluation system for quantifying the long-term effects of goaf backfilling on groundwater stability. The practical engineering application of this integrated technology has been successfully demonstrated at a coal mine in northern Shaanxi Province, where a large-scale demonstration project capable with an annual disposal capacity of 2 million tonnes has been commissioned. This achievement represents a significant improvement in the resource utilization of solid waste and, more importantly, provides both the technical foundation and scientific guidance necessary for coal production bases to achieve the goal of zero gangue discharge at mine sites.