In order to study the differences in microstructure and mechanical properties of three kinds of electrodeposited cobalt plates, the preferred orientation, crystal structure, and microstructure of each plate were analyzed by X-ray diffractometer and scanning electron microscope. Furthermore, the mechanical properties of electrodeposited cobalt plates were tested, including their strength, hardness, and toughness. The results show that all of the plates are pure cobalt phases with a close-packed hexagonal structure (hcp) and random grain orientation. The deposition layer of the A-Co plate is uniform and dense with few holes, while those of the B-Co and C-Co plates grow apart and has a large number of holes. Meanwhile, the average grain size on the surface of the A-Co plate is the smallest, and the grain size distribution of the deposited layer is uniform, while that of the B-Co plate is the largest, and the grain size distribution of the deposited layer is not uniform. The starting sheets of the three electrodeposited cobalt plate cross-sections are all columnar crystal structures, and the growth patterns of the two sides of the starting sheets are different. From the analysis of mechanical properties, it is found that the tensile strength and hardness of the A-Co plate are higher than those of other two cobalt plates, but the toughness is lower. In conclusion, the quality of A-Co plates is significantly better than that of B-Co plates and C-Co plates.