Abstract: The resonance scattering spectra of colibacillus have been studied. It has three resonance scattering peaks at 470 nm, 510 nm and 730 nm. When the excited wavelength λ_ex is at 470 nm(6.38×10¹⁴Hz), the colibacilus solutions exhibit aresonance scattering peak at 470 nm and a 1/2 fraction frequency scattering peak at 940 nm (1/26.38×10¹⁴Hz). A resonance scattering peak at 510 nm was observed as the λ_ex=510 nm. There is a double frequency scattering peak at 365 nm (2×4.11×10¹⁴Hz) and a resonance scattering peak at 730 nm (4.11×10¹⁴Hz) for the λ_ex=730 nm. The fraction frequency peak and the double frequency peak have similar scattering property as the resonance scattering peak. The concentration of colibacillus in the range of 0.074～38×10⁸ cell/mL is proportional to the scattering intensity I₄₇₀、I₅₁₀、I₇₃₀, respectively.