In this paper the magnetic field profiles produced by coil currents of I=115.2A，I=137.7A and I=137.7A with a SmCo permanent magnet under the substrate holder in the deposition chamber and plasma chamber in the single-coil divergent field MWECR(micro-wave electron cyclotron resonance) CVD system was investigated. Then the magnetic field gradient of these magnetic field profiles was obtained quantitatively using Lorentz fit. The results indicated that the gradient value nearby the substrate, which was produced under the condition that the magnetic field profiles are produced by the coil current 137.7A with a SmCo permanent magnet under the substrate holder, is the largest, the larger one being produced by the coil current of 137.7A without the permanent magnet and the smallest one being produced by coil current of 115.2A. The effect of magnetic field gradient on characteristics of a-Si:H film has been also analyzed. It was found that high deposition rate was observed nearby the substrate with a high magnetic field gradient and that the better photosensitivity of a-Si:H film could be obtained at the lower substrate temperature when magnetic field gradient is high.