BACKGROUND: The biocompatibility of chitosan and Nafion can be improved by external factors. OBJECTIVE: To explore the effect of different weak laser irradiations (red, blue, green) on biocompatibility of porous chitosan membrane and the Nafion membrane. METHODS: (1) Porous chitosan membrane test: Forty-eight Sprague-Dawley rats were randomized into red, green, blue light groups (n=16 per group). Porous chitosan membranes (two membranes at each side) were implanted into the bilateral subcutaneous tissue of the rat back with the spine as the axis of symmetry, and then the four implanted membranes in each rat were irradiated by red light for 0, 2, 4, 6 minutes respectively. The irradiation lasted until sample collection at 7, 14, 28 and 56 days after implantation, and the samples were used for histological analysis. The same procedures were done in the blue and green light groups. (2) Nafion membrane test: Twenty-four Sprague-Dawley rats were randomized into red, blue and green light groups (n=8 per group). Nafion membranes (two membranes at each side) were implanted into the bilateral subcutaneous tissue of the rat back with the spine as the axis of symmetry, and then the four implanted membranes in each rat were irradiated by red light for 0, 2, 4, 6 minutes respectively. The irradiation lasted until sample collection at 7 and 14 days after implantation, and the samples were used for histological analysis. The same procedures were done in the blue and green light groups. RESULTS AND CONCLUSION: The content of red blood cells in blood vessels and vascular density around the membrane materials (porous chitosan membranes and Nafion membranes) increased after irradiated by red light (especially at 7 days after implantation); the red light had less influence on the inflammatory response and fibrous capsule thickness around the two kinds of membranes. The inflammatory cells percentage around the membrane materials irradiated by green light for 4 minutes was significantly reduced, and the blue light had less influence on inflammatory responses; blue and green lights showed effects on the fibrous capsule thickness and vascular density around the membrane materials, but the effect was not obvious. Thus, to a certain extent, weak lasers can improve the biocompatibility of PCSM and Nafion membrane.