Based on equivalent particle scattering model, Mie theory is introduced to calculate the scattering phase function, anisotropy factor and scattering coefficient of biological tissue. Numerical results show that the anisotropy factor and scattering coefficients increase with the increasing of the equivalent particle's diameter when the tissue is irradiated by visible light; the anisotropy factor and scattering coefficients decrease monotonously with the increasing of incident light wavelengths when the equivalent particle's diameter is relatively small; the anisotropy factor and scattering coefficients have no monotonicity with respect to the wavelengths when the equivalent particle's diameter is big. The above numerical results explain the published experiments well.