A series of Er３(Fe, Co, M)２９ (M=Cr, V, Ti, Mn, Ga, Nb) compounds has been synthesized and their structure and magnetic properties have been investigates by means of x-ray diffraction and magnetic measurements. It is found that the Fe-based Er３(Fe,M)２９ compounds crystallize in the Th2Ni17-type structure with disordered substitution of the dumbbell Fe-Fe, instead of Nd3(Fe,Ti)２９-type structure, so its chemical formula can also be expressed as Er2－n(Fe,M)17+2n (n=0.2). Substitution of M for Fe in the Er３Fe29 compound leads to an increase in the Curie temperature. With the substitution of Co for Fe in the Er３(Fe,M)２９ (M=Cr, V) compounds, a new phase was found which crystallizes in monoclinic symmetry. The anisotropy of the Er３Fe19.5Co6V3.5 compound at room temperature is of easy-axis type and a spin reorientation transition from the easy-axis type to the easy-plane type anisotropy occurs when temperature decreases to 162K. A first order magnetization process (FOMP) was observed in the HMD magnetization curve of Er３Fe19.5Co6V3.5 at 5K, the critical field of the FOMP was derived to be 3.8T.