Abstract: The crystal of gadolinium pentaphosphate belongs to the monoclinic system.The space group is P_21/a.The crystal parameters are a=12.910(9), b=8.889(10), c=8.721(6)Å, β=90.53, z=4. The diffraction data have been col-lected by using PW-1100Four-Circle Diffractometer. The total number of inde-pendent diffraction amounts to 2012. The structure has been solved by heavy-atom method, and the structure parameters have been refined by means of full matrix and block-diagonal least square method, R=0.103. The result of struc-ture analysis indicated that the coordination number of gadolinium cation is eight,Gd-Gd distance is 5.902Å.