Luminescence characteristies of α-Si∶H thin film oxidized by low-temperature plasma was investigated. Strong blue photoluminescence peaks centered at 460 nm,465 nm,472 nm,478 nm,485 nm,490 nm and 496 nm ranging from 450 nm～500 nm were observed at room temperature. The result shows that strength of the photoluminescence peak increases with the cycle number of deposition-oxidation during preparation. Blue luminescence peaks originate luminescence centers related to O-Si defect.