The invention relates to an all-optical integrated broadband ultrasonic detection device and a preparation method thereof. comprising an L-shaped housing, the L-shaped shell comprises a vertical section and a horizontal section, a first through hole is formed in the vertical section along the vertical direction, a second through hole is formed in the horizontal section along the vertical direction, a circular resonant cavity is arranged at the bottom of the second through hole, the circular resonant cavity is coaxial with the second through hole, the lower end of the circular resonant cavity is flush with the lower end of the horizontal section, and a circular second copper foil is adhered to the lower end of the circular resonant cavity; High-power optical fiber is vertically arranged in the first through hole, and a circular first copper foil is adhered to the lower end of the first through hole; An optical fiber ceramic ferrule jumper wire is vertically arranged in the second through hole. The present invention utilizes optical fiber to transmit nanosecond pulse laser and irradiate copper foil to provide ultrasonic source for ultrasonic detection of rock physical model, utilizes copper foil and optical fiber end face to construct optical interference structure and collect ultrasonic echo; The two parts are stably combined through an optimally designed L-shaped integrated structure and have the characteristics of flexibility and portability.