The invention discloses a fixing device for a vehicle-mounted ultrasonic sensor. The fixing device comprises a bumper (1), an elastic cover ring (2) and a support (4); an installing hole (11) is formed in the bumper (1), the elastic cover ring (2) is clamped in the installing hole (11), a penetrating hole (24) is formed in the elastic cover ring (2), the size of the penetrating hole (24) is matched with that of the probe end of the ultrasonic sensor (3), and the support (4) is fixed to the inner side face of the bumper (1). One end of the elastic cover ring (2) is clamped in a positioning hole (44) of the support (4), and the probe end of the ultrasonic sensor (3) penetrates through the positioning hole (44) and is fixed in the penetrating hole (24). The fixing device for the vehicle-mounted ultrasonic sensor is simple in structure and convenient to install.