The effect of Co substitution and stabilizing elements on the structure and magnetic properties of Nd3Fe29-x-yCoxMy(M=Ti,V,Cr) compounds was investigated by means of x-ray diffraction and magnetic measurements. The results show that all the synthesized compounds have been crystallized in Nd3(Fe,Ti)29type structure with monoclinic symmetry and space group A2/m. The solution of Co element in the compounds is different for the different stabilizing elements. For Cr as the stabilizing element, the pure Co-based 3:29 phase could be obtained and the higher Cr content is required to stabilize the phase with increasing Co content. For Ti and V, the solution of Co in the compounds could be only 6.63 and 12 atoms, respectively. All the Nd3(Fe, Co, M)29compounds show easy-planar type anisotropy at room temperature. For the Nd3(Fe,Co,V)29compounds, the Curie temperature and saturation magnetization increase first and then decrease with further increasing Co content. The spin reorientation temperature shows and increasing tendency except the minimum for x=6 due to the preferential occupation of Co atoms. For the Nd3(Fe, Co, Cr)29compounds, the Curie temperature increases first and then decreases with increasing Co content, but the magnetization is diffcult to be saturated and only shows a decreasing tendency. The spin reorientation transition was only observed for the samples with x=0 and 6.