To address the misplacement of fine particles in the underflow caused by structural defects in conventional hydrocyclones, a composite column-cone hydrocyclone (C-C hydrocyclone) was proposed, featuring a cone-column-cone structure. Computational Fluid Dynamics (CFD) techniques were employed to study the diameter ratio and various configurations of C-C hydrocyclone, assessing the impact on separation performance. Results indicated that increasing the column section diameter ratio from 0.5 to 0.7 reduced the cutting size by 22.96 %, enhanced sharpness by 9.87 %, and improved separation efficiency. These findings offer valuable insights for the design and application of C-C hydrocyclones based on specific requirements such as grinding classification and flotation operations.