The Chan-Vese (CV) model has been widely investigated for breast ultrasound (BUS) image segmentation. However, the traditional CV model can not meet the requirement of high precision and speed for BUS segmentation. To address this issue, an improved CV model based on the ratio of exponentially weighted averages (ROEWA) operator was proposed in this paper. Firstly, the ROEWA of the BUS image was calculated. Then, a ROEWA-based edge indicator function was built to replace the Dirac term of traditional CV model. Finally, the smoothing term was removed to improve the speed of curve evolution. Experimental results show that the advantages of the proposed model in terms of computational efficiency and accuracy.