Gravity separation is the primary method used to beneficiate Ta-Nb-bearing minerals, however, it performs poorly in low-grade and fine-grained ores. A comparative study of gravity separation products (concentrate, middlings, and tailings) reveals the factors affecting the separation behavior of Ta-Nb-bearing minerals in the process combined with a spiral chute and shaking table from the perspective of mineralogy. The results reveal that columbite-tantalite is the principal Ta-Nb-bearing mineral. As the grinding time increases, the grade of Ta and Nb in concentrate increases significantly. The grain size of columbite-tantalite in the concentrate is the coarsest, followed by that in the middlings, and the finest in the tailings, which are mainly distributed in the range of -150+38 μm, -75+20 μm, and -38 μm, respectively. The liberation degree of columbite-tantalite in the concentrate and tailings is positively correlated with grinding time, while that in the middlings is negatively correlated with grinding time. The density of columbite-tantalite-bearing particles in concentrate is mainly distributed above 3 or even 4, due to the high liberation degree of the columbite-tantalite in the concentrate, as well as the high amount of rich intergrowth associated with heavy minerals. The density of Ta-Nb-bearing mineral particles in the middlings and tailings is predominantly distributed in D<3, owing to columbite-tantalite mainly associated with lighter gangue minerals such as quartz, albite, and orthoclase. It demonstrates that the liberation degree is not the most essential factor in determining columbite-tantalite separation behavior in the gravity field, and the mineralogical characteristics of columbite-tantalite including grain size, association relationship, and particle density, may be more important. The results of this investigation can provide theoretical support for the strengthening separation of low-grade tantalum-niobium ore.