The invention discloses a photoacoustic computed tomography system based on an adjustable focusing type optical fiber sensor. The photoacoustic computed tomography system comprises a short-pulse laserdevice, a reflector, a beam expander, a water tank, a to-be-measured object, an optical fiber clamp, the adjustable focusing type optical fiber sensor, a rotary stepping motor, a photoelectric detector, a data collecting card and a computer and is characterized in that the short-pulse laser device emits short-pulse laser which irradiates the to-be-measured object, the to-be-measured object generates an ultrasonic wave due to a photoacoustic effect, the optical fiber sensor receives the ultrasonic wave and converts the same into an optical signal, the optical signal is processed by the photoelectric detector and the data collecting card and transmitted to the computer for reconstruction to obtain a two-dimensional tomography image, and a linear translation platform controls the to-be-measured object to move axially to obtain a three-dimensional tomography image. The adjustable focusing type optical fiber sensor is simple in structure, adjustable in curvature, high in sensitivity and suitable for being used in the photoacoustic computed tomography system.