To address the issue of coarse particle mismatch in the overflow, this study proposes a self-adaptive hydrocyclone with overflow adjustment. By designing a conical vortex finder and a spring-loaded ball back pressure structure to achieve a size-adaptive adjustment of the vortex finder based on separation conditions. This study conducted a single-factor experiment to investigate the effects of feed pressure, feed concentration, and underflow port diameter on the separation performance of the hydrocyclone. The test results show: The centrifugal force within the hydrocyclone strengthened as the feed pressure increased, the solid yield of the underflow increased, and the separation efficiency curve shifted to the left. As the feed concentration rose, the content of coarse particles in the overflow increased, the cut size increased by 2.4 μm, and the separation performance decreased significantly. The hydrocyclone exhibits a high separation efficiency when the underflow port diameter is 12 mm.