By simultaneously scanning both the excitation and emission monochromators of a common spectrofluorometer with same starting excitation and emission wavelength (namely, Delta lambda = 0), we obtained synchronous light scattering (SLS) signals that related to Rayleigh and Mie scatterings. It was found that the SLS signals could be applied for quantitation and differentiation of model bioparticles such as Saccharomyces cerevisiae, Schizosaccharomyces pombe, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium. In PBS buffer, these model bioparticles could form colloidal suspensions or dispersions of sizes ranging from hundreds of nanometers to tens of micrometers, giving SLS signals with the intensity being proportional to the amount of bioparticles in the range from 1.7 x 10(5) to 1.7 x 10(9) CFU/mL. A further finding is that polarized synchronous light scattering (PSLS) signals Of I0 degrees-30 degrees. against I0 degrees-0 degrees, which could be obtained by introducing polarizing sheets accessory of the spectrofluorometer, and the derivative synchronous light scattering (DrSLS) signals, which could be obtained directly with the extension function of the spectrofluorometer, offer differentiation information of bioparticles connected with their size, shape, refractive indexes, and inner structure. Refractive indexes of spherical bacteria were then calculated based on light scattering signals.