The stimulated Raman scattering mode competition in hexamethylene(C6H12) pumped by different wavelength is observed. The high-gain Raman mode is determined by the pump wavelength. The Raman mode ω2(2852—3038cm-1) is generated when pumped by short wavelength(404, 532nm)laser, while the Raman mode ω1(802 cm-1)　is generated when pumped by the long wavelength (808nm)laser. Similar phenomenon is generally observed in Raman experiments. The mechanism of the phenomenon and its possible application are discussed.