Abstract: The feasibility of using photoacoustic spectral parameters to evaluate chronic prostatitis is explored. A chronic prostatitis model in rats was established by injecting Freund’s complete adjuvant. Prostate tissue sections were scanned using a photoacoustic microscopy instrument to acquire raw photoacoustic signals. Spectral parameters of the signals (slope, intercept, average spectral power, spectral centroid shift) were calculated, analyzed, and statistically evaluated, followed by parameter imaging. The influence of selecting different frequency bands on the evaluation results was also discussed. Experimental results indicate significant differences in the statistical and imaging results of spectral parameters between inflammatory and normal tissues. Imaging using spectral centroid shift (SCS) can differentiate between inflammatory and normal tissues. Moreover, under fixed bandwidth conditions, the slope parameter and average spectral power parameter yield clear imaging results in the high-frequency and low-frequency spectral ranges, respectively, with minimal influence of different frequency bands on the imaging of the intercept parameter.