Abstract: Silicon carbonitride (SiCN) films were prepared with microwave electron cyclotron resonance plasma enhanced unbalance magnetron sputtering technique (MWECR PEUMST). FTIR and XPS characterization results indicate that the amount of CSiN subchemical structure in deposited film increases from 14.3% to 43.6%, when the silicon target sputtering power increases from 150W to 350W. Moreover, larger N2gas flow rate is beneficial to the formation of sp2C＝N and sp1C≡N chemical structure. The optical gap of deposited SiCN films deduced from the Tauc method shows that the maximum optical gap of 2.8eV can be obtained when the silicon target sputtering power is 300W, the carbon target sputtering voltage is 600V and the N2 gas flow rate is set at 6sccm.