Numerous novel algorithms have been proposed in the fields of steganography with the goals of increase security,capacity and imperceptibility. In this paper, we introduced a new blind adaptive algorithm in image steganography technique to Improving that goals. The existing methods hide the information using constant bit length in integer wavelet coefficients. This paper uses variable bit length based on float wavelet coefficients to hide the data in a particular positions using secret key. The proposed method try to obtain an optimal mapping function to reduce the difference error between original coefficients values and modified values. we provided with the double security by using a secret key only known to both sender and receiver, therefore improving goals compared to the existing algorithm.