The condition of blood circulation plays an important role in the development of the disease. In order to monitor the tissue microcirculation of the brain, gastrointestinal tract and other important organs in animal models with a large field of view, and obtain the blood vessel structure and oxygenation function information of target tissues with high sensitivity, high resolution and high contrast, a photoacoustic microscopic imaging technology based on optical fiber ultrasonic sensor was proposed in this paper. In this technology, the orthogonal dual-frequency fiber laser independently developed by our research group is used as the ultrasonic sensor. Different from the traditional piezoelectric ultrasonic sensor, the fiber laser ultrasonic sensor is small in size and carries out ultrasonic sensing in a non-focusing way, which can ensure the detection sensitivity while realizing the large field of view ultrasonic detection. The combined scanning mode of galvanometer and motor is designed, which can realize the large-field imaging of the vascular structure of animal model. Using 532 nm pulsed laser with high power and high repetition frequency as seed light source, on the basis of 558 nm pulsed laser obtained by optical fiber stimulated Raman scattering effect, the blood oxygen saturation information of blood vessels in animal tissues was obtained by dual-wavelength excitation method of 532 nm and 558 nm by utilizing the difference of hemoglobin absorption spectrum under different blood oxygen saturation. The imaging results were able to distinguish arteries and veins by different blood vessel colors. By vertically scanning the edge of the surgical blade, the resolution of the large-field optical fiber photoacoustic microimaging system was determined to be 4.2 μm. A wide range of photoacoustic functional imaging was performed on the cerebral cortex of mouselet under anesthesia, and the differential effects of different anesthetics on the hemodynamics of live animals were observed, that is, the venous oxygen saturation of live animals under isoflurane and oxygen mixed gas anesthesia was higher, while the arterial blood oxygen saturation was slightly lower than that of pentobarbtal sodium injection. In addition, the changes of microcirculation status on the intestinal surface of rats with anaphylactic shock were studied by wide-field imaging. Abnormal changes of blood circulation function were observed during anaphylactic shock, that is, the mean blood oxygen saturation of venous vessels on the surface of small intestine of rats with shock was lower than that in normal state, and the blood vessels were dilated. The mean blood oxygen saturation of arterial vessels increased, the blood vessels dilated, and the total blood vessels decreased. These results provide effective information for the study of the effect of anaphylactic shock on microcirculation. Experimental results of scanning imaging in animal models show that the system can visualize changes in microcirculatory dysfunction in living animal tissues with single-vessel spatial resolution in the range of centimeters, while obtaining hemodynamic information of blood vessel structure (including blood vessel diameter, blood vessel density), hemoglobin concentration and blood oxygen saturation. This technique provides a new technical means for clinical study of the changes of blood circulation during the occurrence, development and treatment of diseases.