This paper presents an improved diameter bisection method used in the application of ellipse detection. Based on first and second order derivative grouping and multi-weight, the proposed diameter bisection method offers significant speed improvement of ellipse detection over other chord tangent methods based on Hough transform. The computation complexity of the algorithm is formulated and the results show that the proposed algorithm offers a very good performance. Compared to other Hough transform-based methods, the proposed method is much simpler and thus faster. When compared with original diameter bisection, the proposed method improves on the robustness, speed, and accuracy through the use of multi-weights and newly introduced constraints.