Encoding is one of difficult problem of research on genetic algorithm (GA). Float code (FC) is super to other codes in function and restriction optimization. But it was ignored by researchers how FC was denoised in running environment of GA for enhancing the performance of GA. In this paper, it was proved by the wavelet theory that odd-length and even-length of chromosome encoded could all mutate with wavelet denoising. The float code GA (FCGA) with orthonormal multiwavelet denoising mutation (FGAWDM) was presented by it based on the above result. The experiments were done by it. The result indicates which FGAWDM is superior to FCGA.