Hydrogenated microcrystalline silicon (μc-Si:H) thin films have been grown on glass substrates by electron cyclotron resonance chemical vapor deposition (ECR-CVD) at a low temperature of 180 °C. We investigate the influence of hydrogen dilution ratio (H2/SiH4) and working pressure on structural properties as deposition rate, crystallinity, and hydrogen content of the μc-Si:H. It is found that with increasing hydrogen dilution ratio and decreasing the working pressure, the deposition rate and the hydrogen content decrease, while the crystallinity increases. The phenomenon is attributed by the etching effect of hydrogen atoms, which will break the weak bonds to form an order structure. Furthermore, we have obtained high crystallinity under low hydrogen dilution ratio and low temperature. We have demonstrated that high-crystallinity μc-Si:H thin films can be grown under much lower hydrogen dilution ratio compared with conventional PECVD method by ECR-CVD due to the high plasma density.