By chitosan as a stabilizer and reducing agent, the tunable surface plasmon resonance (SPR) ab- sorption peak of gold nanoplate has been successfully fabricated by water bath heating of solution containing HAuCl4, chitosan and gold nanoseeds. The SEM images indicated that the gold nanoplates were mainly composed of triangular and truncated triangular shape. The edge is about 170 nm. X-ray diffraction analyses indicated that the gold nameplates were pure single crystals with {111} planes as their basal planes. The growth mechanisms on synthesis of chitosan-mediated gold nanoplate were discussed. Under optimum con- ditions the SPR absorption peak of gold nanoplate in-plane dipolar is 920 nm. The experiment results showed that the near-infrared SPR absorption peak and the absorption intensity can be effectively controlled by controlling the amounts of chitosan and gold seeds, water bath temperature and bath time.