In this paper, an electronic signature algorithm, using a combined technology of digital signature, digital watermarking and time stamp, is presented. In this algorithm timestamp information is added to digital signature data, improving the signature safety and anti- offensive. A digital watermark embedding algorithm based on wavelets transform module maximum is designed. Using this algorithm the signature information can be embedded into the signature image as a watermark, enhancing the signature information hidden. The experiment shows that the algorithm can meet very well the requirements of contract signature in e-commerce transactions. This algorithm not only implements authentication, but also ensures the integrity and non-tampering of the contract.