Unbalanced magnetron sputtering (UBMS) is used to deposit mechanical and optical coatings due to the advantages of high deposition rate and low pollution level, but the low utilization rate of the target material limits its applications for industrial-scale production. To improve target utilization during UBMS, a magnetron system combining a coil magnet and a permanent magnet has been developed. The effects of the operating parameters of the magnetic flux density on the magnetic field were investigated, and the erosion profiles on the target surface were examined in terms of the plasma distribution. It was found that the erosion center was located where the lines of magnetic induction were parallel to the target surface. A strategy of changing the current of the central coil was finally proposed, which improved the target utilization to 52.9 %. These results provide theoretical guidance to improve the target utilization of UBMS by optimizing the design of the cathode target and magnetic field.