Fluorescence imaging technique is an important technique for noninvasive detection of latent fingerprints. An ultraviolet (UV) laser is used as excitation light source, and the thermal treatment technique and the fluorescence imaging technique are combined to noninvasively detect and show the latent fingerprints on the surface of porous papers. By controlling the heating temperature and time in the thermal treatment period, the brightness contrast between fingerprints and background is increased, and the fresh and aged latent fingerprints on the paper surface are noninvasively detected and shown by using the fluorescence imaging technique. The study provides experimental guidance for the application of thermal treatment and fluorescence imaging techniques in the field of latent fingerprint detection.