Using low-pressure plasma chemical vapor deposition （LPPCVD）, with trans-2-butene and hydrogen as the precursors, we have successfully deposited 30 μm CH coatings on microshells in intermittent bounce mode .The surface finish was measured by atomic force microscopy （AFM）, It was found that the surface finish was improved greatly with reduced duty ratio. When the duty ratio was 1/5, the surface roughness was less than 30 nm for the 30 μm thick a-C:H film. Uniformity of a-C: H films were measured by X-rayradiography. The results showed that the influence was little of duty ratio to the uniformity of a-C: H film. When the duty ratio was 1/7, microshells could not keep on bouncing.