The invention relates to a voice message pushing method, an on board unit, and an electronic toll collection system. The electronic toll collection system comprises the on board unit (OBU), a road side unit (RSU), and an information service platform server, the on board unit (OBU) comprises a micro-controller MCU module, a speech driving circuit module, and a loudspeaker electrically connected with the speech driving circuit module, and the micro-controller MCU module controls the speech driving circuit module to convert information received by a radio frequency transmission and reception module to audio signals so that the audio signals are recovered to voice for playing through the loudspeaker. According to the method, the on board unit, and the electronic toll collection system, through the road side unit (RSU), data communication is accomplished, the vehicle position and the driving direction are located, reliable guarantee is provided for information screening, useless information is effectively blocked, information is provided for each vehicle equipped with the on board unit (OBU) in a targeted manner, and vehicle drivers can drive in an attentive manner and select the fastest path to arrive at the destination.