A novel kind of waveguide multilayer memory (WMM) device consists of a stuck of slab optical waveguides.In WMM,the data are recorded in the form of waveguide defects and are read out by using the light scatter effect of the waveguide defects.Experimental result with a 10 layer device demonstrated that the WMM is a very promising three-dimensional optical storage technology possessing the advantages of the high SNR in the layer and the small cross talk between the layers.