Water is a special medium. In the underwater laser image there are always speckle noise which is caused by backscattering of water. A multidirectional morphological filtering algorithm is proposed by use of the characteristics of morphology's multisolution analysis and fastly-computing. It can not only efficiently reduce the speckle noise but also preserve the detailed features of the image. Experimental results indicate this algorithm is a fast efficient algorithm to filter speckle noise in the underwater laser image.