Diamond has many excellent physical, chemical, mechanical, optical, thermal, and electrical properties such as high hardness, extreme chemical inertness, low friction coefficient, wide optical transparency bandwidth, high thermal conductivity, and wide band gap. Therefore, diamond can provide potential solutions to many advanced engineering problems. The reactive ion etching (RIE) method was adopted in this research to etch the CVD diamond using oxygen as the etchant gas. The Au and Pt were used to form micro-mask on CVD diamond film. Three techniques namely photo-lithography, laser selectively removal and reflow method were employed to generate the micro-masks. The etching parameters and the forming mechanism of microstructures were investigated in this study. Field emission scanning electron microscope (FESEM), α-step profiler, and Raman spectrometer were used to observe and analyze the morphology, surface roughness and chemical composition of the obtained microstructures. The results showed that microstructures could successfully produce by the proposed RIE method and the au mask tended to produce pillar-shaped microstructures and Pt mask helped to form vertical sidewall.