The study proposed a parabolic hydrocyclone to solve the problem of excessive fine particles in the underflow, namely, fine clipping underflow during classification of red muds. Experimental studies on separation performance differences, particularly the yield, product concentration, particle size, and stage efficiency, between hydrocyclones with parabolic and straight cones were carried out, and the influence of the apex diameter on the separation performance of the parabolic hydrocyclone was studied. Based on this result, a regression model for the content of -5 mu m particles in the underflow was established, and the accuracy of the regression model was validated. The experimental results show that the content of the -5 mu m particles in the underflow of the hydrocyclone with a parabolic cone was reduced by 9.7% as compared to that of the hydrocyclone with the straight cone, thereby indicating that the parabolic cone effectively decreased the number of fine particles in the underflow. According to the regression model, the optimal operating conditions of the parabolic hydrocyclone exhibited a solid concentration of 29%, an apex diameter of Phi 5 mm, and a feeding pressure of 0.08 MPa. Under these conditions, the underflow of the hydrocyclone with a parabolic cone presented a 17.1% content of -5 mu m particle, which was 15.2% lower than that in the underflow of the hydrocyclone with a straight cone.