Abstract: The solid-bridge force of ash has significant impact on the ash deposition behavior. The model of nondimensional neck tensile strength of ash was developed by the nondimensionalization of the solid-bridge force measurement results. The calculation results agreed well with the experimental results, and the deviation was less than 22%. The ash neck tensile strength was only 1/150 of the material tensile strength when at relatively low temperatures, which disproved the applicability of the traditional estimation method for ash.