Abstract The structural and magnetic properties have been investigated by means of X-ray diffraction and magnetization measurements. The Dy2AlFe16-xMnx compounds have a hexagonal Th2Ni17-type st ructure. The thermal expansion of Dy2AlFe16-xMnx (x=1 and 2) compounds have been investigated by X-ray dilatometry in the tempe rature range 104—647K. The results show that there is a thermal expansion anoma ly at low temperature and a negative thermal expansion near the Curie temperatur e. There exists a strong and anisotropic spontaneous magnetostriction in the mag netic state of Dy2AlFe16-xMnx compounds. The sp ontaneous volume magnetostrictive deformation at low temperature decreases with increasing x. The result of magnetization measurement shows that the Curie tempe rature and the spontaneous magnetization of Dy2AlFe16-xMn< sub>x compounds at 5K decrease rapidly with increasing x.