The present invention provides a message broadcast system and method for vehicular network. The system comprises a positioning device, a transmitting device and a processing device. The positioning device positions a location data of a vehicle. The transmitting device transmits a first packet to a neighbor vehicle. The processing device is coupled to the positioning device and transmitting device. The processing device determines the transmitting device transmits a second packet to the neighbor vehicle when the vehicle is in a section of crossroads. The processing device determines whether the vehicle is in a section of crossroads or a road section according to a third packet periodically transmitted from the neighbor vehicle.