Abstract: Several CVD diamond films were etched using ECR plasma in different magnetic fields and working pressure. Double probe and ion sensitive probe were used to investigate the influence of magnetic field and working pressure on etching effect. Results showed that when the divergence magnetic field was changed to the convergence one, the ion temperature, the electron temperature and the plasma density increased and the etching effect was enhanced. While the working pressure changed from a low pressure to a high pressure, the plasma parameters first increased and then decreased, a drop of the surface roughness was showed as the same trending.