Ultrasonic flow sensor

The invention relates to the technical field of flow monitoring equipment, in particular to an ultrasonic flow sensor. The sensor comprises a sensor auxiliary part used for being connected with a process pipeline; and a main measuring part which comprises a base and an instrument mechanism, the instrument mechanism is installed on the base, and the base is installed on the sensor auxiliary part. According to the scheme, the instrument mechanism which is prone to position deviation and is not resistant to high temperature is installed on the base in advance to form the main measuring part, and after the sensor auxiliary part is welded to the process pipeline, the base loaded with the instrument mechanism is installed on the sensor auxiliary part. On one hand, damage of high welding temperature to the instrument mechanism can be avoided; and on the other hand, the problems that the instrument mechanism displaces in the secondary assembly process, the effective sonic path distance of the sensor is changed, the m