For compensating the shortcoming of multibeam sonar image in resolution and that of side scan sonar image in position, and meeting with the requirement of acquiring high\|quality seabed relief image in practice, a new method, by merging MBS image and SSS image and forming high\|quality seabed relief image, is presented. Firstly, speeded\|up robust feature (SURF) algorithm is studied deeply and an improved algorithm ISURF is given out. The ISURF algorithm obviously improves the matching accuracy and decreases the matching time of MBS image and SSS image relative to SURF algorithm. Then, four image\|fusion algorithms are studied. By comparing and analyzing in virtue of independent evaluation parameters and associated evaluation parameters, the optimum image fusion method, which is Laplace Pyramid method or wavelet transform method, is given out for fulfilling the fusion of MBS image and SSS image. Based on above researches, a complete fusion procedure of MBS image and SSS image is presented and used for forming a high\|quality seabed relief image. These methods depicted in this paper have been proved by experiments.