The invention discloses a rotary water immersion ultrasonic transducer. The device comprises a hollow mandrel, a probe, a positive pole slip ring, a negative pole slip ring, a core sleeve, bearings, ashell and a brush wire cable; the probe is arranged on the outer wall of the mandrel; the positive pole slip ring and the negative pole slip ring sleeve the mandrel; the core sleeve is arranged between the positive pole slip ring and the negative pole slip ring and used for insulating the positive pole slip ring from the negative pole slip ring; the shell sleeve the outer sides of the bearings ofa sliding sleeve combination; the brush wire cable penetrates from the outer side of the shell to the inner side of the shell and is communicated with the positive pole slip ring and the negative pole slip ring; the inner rings of the bearings are fixedly connected with the mandrel; the sliding sleeve combination is clamped between the two inner rings at the two ends of the sliding sleeve combination and synchronously rotates along with the inner rings; and the outer rings of the bearings are fixedly connected with the shell. The high-frequency water immersion point focusing energy converteris a narrow-pulse broadband energy converter. The rotary water immersion ultrasonic transducer and an energy converter assembly can be assembled together so as to carry out high-speed rotation detection. During detection, a to-be-detected pipe penetrates into the mandrel; the focus of the energy converter is located on the pipe wall of the to-be-detected pipe; and it is guaranteed that the excitation and receiving of electric signals are stable during the high-speed rotation of the energy converter through the contact of the brush wire cable and the slip rings.