Abstract: By using neutron scattering technique, a series of LaNi5－xAlx(x＝0.1, 0.25, 0.3, 0.45, 0.5, 0.75) alloys and their deuterides were studied at room temperature. A series of experimental data of LaNi5－xAlx alloys were refined by means of program FullProf. Their space groups are found to be P6/mmm. The alloys’ lattice parameters, cell volumes and atomic positions were obtained. It is discovered that Al atoms just substitute a part of Ni atoms which are at 3g position. Furthermore, it is also learned that the variety of cell volume is almost proportional to the content of Al atoms in the alloys. The refined results of LaNi5－xAlxDy diffraction data show that the deuterides’ space groups are still P6/mmm. The varieties of phase components, lattice parameters and cell volumes were analyzed after charging deuterium. Afterwards, the atomic positions and distribution of deuterium atoms in the cell were obtained.