Abstract: Diamond films were prepared on the surface of silicon wafers by pulse bias and DC bias assisted hot wire chemical vapor deposition.The effects of two kinds of bias on the surface morphology and quality of the films were stud-ied.The morphology and quality of the films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy,and the gas chemical reaction during the film growth was analyzed by plasma spectroscopy.The results show that the size of the two kinds of bias has a great influence on the morphology and quality of the film.Compared with the DC bias method,the diamond film prepared by pulse bias method have larger grain size,better uniformity and smaller internal stress.When the bias voltage is too high,the surface grain edge will appear electron flow bombardment eaching,which occars at DC bias voltage is lower than pulse voltage,indicating that the continuous electron stream bombardment at DC bias voltage is more likely to lead to etched grain edge.Grain refinement occurs with secondary nucleation at high bias pressure.Spectral diagnosis results show that the main reason for these differences is that the strength of the active group increases with the increase of the bias,and the concentration of the active particles can be stronger.