Abstract: The vortex shedding frequency spectrum characteristics on a heated circular cylinder in water cross flow was investigated experimentally.Heating changed the Fourier transform frequency spectrum energy of vortex shedding signal.The effect of heat varied with Reynolds number and there existed a critical value Re_L,about 8.84×10⁴ in the test condition.If the flow Reynolds number was less than ReL ,the effect of heat on the Fourier transform frequency spectrum peak value of vortex shedding signal was small, and if the flow Reynolds number was larger than Re_L , the effect of heat would be larger.When the flow Reynolds number was larger than Re_L,heating reduced the Fourier transform frequency spectrum peak value reduce by about 30%.The phenomenon made the vortex shedding unstable and destroyed the Karmen vortex in the wake under some condition, and resonance was induced easily.Generally it arised if the flow Reynolds number be changed but the cylinder undeated.