Structure and magnetic properties of (Nd1-xErx)2Co15.5V1.5compounds have been investigated by means of x-ray diffraction and magnetic measurements. The results obtained show that the (Nd1-xErx)2Co15.5V1.5 compounds crystallize in the Th2Zn17type structure for lower Er content(x0.5). The two structures coexist in the samples with x=0.4 and 0.5 The lattice constants a and c, and the unit cell volumeV show a decreasing tendency with increasing Er content in both structures. With increasing Er content, at room temperature, the anisotropy of the (Nd1-xErx)2Co15.5V1.5 compounds changes from the easycone type for low Er content(x0.5). The spin reorientation transition is observed for the compounds with x=0.0—0.5, and the spin reorientation temperature Tsr shows a decreasing tendency with increasing Er content. In addition, the Curie temperature TC and saturation magnetization Ms also decrease monotonically with the Er substitution for Nd in (Nd1-xErx)2Co15.5V1.5 compounds.