Amorphous InGaZnO (a-IGZO) films were prepared by radio frequency magnetron sputtering, and as-deposited a-IGZO films were treated with plasma in plasma-enhanced chemical vapor deposition equipment. The effects of plasma surface treatment on the microstructure and the optical and electrical properties of IGZO films were investigated. X-ray diffraction analysis indicated that the IGZO films were amorphous. Results showed that plasma surface treatment have remarkable influence on the resistivity, carrier concentration, and carrier mobility of IGZO films. The analysis of x-ray photoelectron spectroscopy revealed a correlation between the electrical properties of IGZO films and plasma surface treatment. For all the samples, the average transmission in the visible region is more than 80%.