A method of using ultrasonic to measure oil pressure in pipeline was described.The special pressure regulating equipment was used to apply pressure to the hydraulic oil in the steel pipe.The broadband ultrasonic transducer with center frequency of 4 MHz was used to detect the hydraulic oil in the pipe on the outer wall of the steel pipe and the reflected ultrasonic echo signal was obtained.Then the short-time Fourier transform (STFT) was used to analyze the ultrasonic echo signal under different pressures.The time-frequency spectrum was compared with the time-amplitude spectrum under same pressure.The results show that with the increase of the hydraulic oil pressure in the steel pipe,the ultrasonic velocity increases and the sound attenuation coefficient increases.After fitting the relationship between the oil pressure in the pipeline and the ultrasonic velocity and the acoustic attenuation coefficient,the function was obtained.The measured ultrasonic velocity and the acoustic attenuation coefficient could be brought into the function to invert the oil pressure.