Using x-ray diffraction and magnetic measurements, we have studied the structural and magnetic properties ofDy2Co17-xMnx (x＝0～5) compounds with a rhombohedral Th2Zn17-type structure. With an increasing Mn concen-tration x, the unit-cell volume V was found to increase linearly. The Curie temperature TC decreases linearly, andthe saturation magnetization Ms at 5K first increases slightly for x ＜1, then decreases rapidly for x ＞1 with a furtherincrease of Mn concentration x. In compounds for x＝1～3, a spin reorientation was found. A magnetic diagram of thecompounds is given.