The invention discloses a vehicle-mounted Bluetooth positioning system and a positioning method thereof, and relates to the field of Bluetooth positioning, the positioning system comprises a user mobile device terminal, a vehicle-mounted Bluetooth terminal and four Bluetooth beacon anchor points arranged in a rectangular shape on a vehicle body; the Bluetooth beacon anchor point and the vehicle-mounted Bluetooth terminal are connected to a vehicle-mounted network. The positioning method comprises the following steps of enabling Bluetooth beacon anchor points to respectively send RSSI (ReceivedSignal Strength Indicator) outwards, collect other RSSI and send the RSSI to a user mobile equipment terminal; after the user mobile equipment terminal collects RSSI of the Bluetooth beacon anchor point, filtering RSSI data; calculating the calculation distances between the anchor points and between the anchor points and the user mobile equipment terminal, calculating a correction factor according to the actual distances between the anchor points, and correcting the calculation distances; and establishing a coordinate system, and performing positioning by using a double-triangle centroid positioning algorithm to obtain the position of the user mobile device. The system and the method have the advantages of being simple in hardware topological structure, small in required calculation datasize, high in real-time performance, small in external environment influence, accurate in positioning and the like.