The invention discloses a single-hole mounting flange for an oil mass sensor. The single-hole mounting flange comprises a rotator, an oil mass sensor shell, a flange nut and a plurality of claws, wherein a central through hole and a sliding slot are formed on the rotator; the bottom end of the oil mass sensor shell extends out of the central through hole of the rotator; a base plate is fixedly arranged at the bottom end; a pin hole is formed on the base plate; the claws are arranged between the base plate and the rotator; a pin shaft which is in matched connection with the pin hole is formed on an end face of each claw; a sliding shaft capable of sliding along the sliding slot is arranged on the other end face of each claw; the flange nut is connected with the rotator through a thread. According to the invention, the fastening mounting can be realized by only drilling one hole on an oil tank, the mounting process is simplified and the production efficiency is increased.