An improved differential evolution (DE) that incorporates a wavelet-based mutation operation to control the scaling factor is proposed. The wavelet theory applied is to enhance DE in exploring the solution spaces more effectively for better solutions. A suite of benchmark test functions is employed to evaluate the performance of the proposed method. It is shown empirically that the proposed method outperforms significantly the existing methods in terms of convergence speed, solution quality and solution stability. ; Department of Electronic and Information Engineering ; Refereed conference paper