Small-angle X-ray and neutron scatterings can measure the structure factor of dispersed particles (macromolecules or colloidal particles), which can estimate the pair distribution function and the pair potential between the particles. However, the assumption of a model pair potential is usually necessary in the estimations. Especially when the system condition is complicated, one cannot prepare a plausible model pair potential. Hence, we propose a model-potential-free method. The new method does not require the assumptions of rigid particle surface and random phase approximation unlike the conventional model-potential-free method.