Squeeze film flow of viscoplastic Herschel-Bulkley fluids between two parallel circular plates under a constant load was analyzed theoretically to derive an approximate solution. This solution was used to determine the yield stress（ζ_o） and Herschel-Bulkley parameters (n, η_HB) of two test materials from their experimental squeezing curves. The results showed that the simple squeeze film apparatus could be used to determine the yield stress and other rheological properties of viscoplastic materials.