Visible light communication (VLC) technology has broad application prospects ,but it is complex with high cost.Narrow band－pass amplifier circuit can simpli fy the s ystem and improve the signal gain and signal-to-noise ratio.In this work,we us e a few components to construct a narrow band－pass amplifier circuit to establish a uni directional VLC system.It is found that the spectral ch aracteristics of the digital pulse interval modulation (DPIM) can be achieved by employi ng relatively narrow bandwidth data transmission.The unidirectional VLC system u ses LED as the data carrier, and avalanche photodiode (APD) as the photosensitive device.The experimental res ults show that the VLC system can realize the unidirectional data transmission w ith the transmission rate of about 45.8kbit/s in the 5m direct sight distance.The des ign has good stability,low cost,and good application prospect.