The invention discloses a flexible integrated ultrasonic transducer, which is integrated by an organic thin-film transistor and a piezoelectric sensor. The flexible integrated ultrasonic transducer consists of a substrate, a moisture-proof isolation layer, a source drain electrode, a semiconductor thin-film layer, a gate dielectric layer, a gate electrode layer, an electrical signal coupling layer, a piezoelectric film layer, an electrode layer and an ultrasonic coupling layer in turn. In order to conveniently prepare a two-dimensional flexible ultrasonic transducer array, a layer of silicon dioxide thin film is deposited on a PET substrate and is used for isolating moisture. The piezoelectric material serving a PVDF thin film of an ultrasonic transducer has the advantages of good piezoelectric performance, low acoustic impedance, and good acoustic impedance matching with water and organisms. Therefore, the sensitivity is improved and the frequency band is widened. High flexibility ofthe PVDF thin film provides good technical basis for integrating the piezoelectric sensor. By adopting the organic thin-film transistor as a built-in signal amplifier, the gain and signal-to-noise ratio are increased, and the anti-jamming capability is improved.