Single crystals of La1.7Ca0.3NiO4 were grown by floating zone method. The crystal structure was determined by single crystal X-ray diffraction. La1.7Ca0.3NiO4 crystallizes tetragonal in space group I 4/mmm (No. 139) with a = 3.833(1) and c = 12.604(4) Angstrom. The stability of the structure is proved down to 125 K.