A vehicle blind spot detection system may include a rearview mirror and an indicating unit. The rearview mirror has a shell and a mirror, and a transmitting area is formed on the mirror. The indicating unit installed in the shell is horizontally aligned with the transmitting area of the mirror. The indicating unit comprises a light-guiding base and a circuit board, and a front side of the light-guiding base has a recess to form a first housing, a light-gathering room, and a second housing therein. A first light emitter and a second light emitter are respectively mounted on the circuit board, and the circuit board has a through hole. When the circuit board is coupled on a rear side of the light-guiding base, the first light emitter and the second light emitter are respectively accommodated in the first housing and the second housing.