In this paper, a hemisphere-shaped soft fingertip for soft fingers is developed and its modeling based on force distribution is presented. We first analyze the geometrical relation of the soft fingertip when it is deformed. Secondly, the force distribution of the soft fingertip is investigated by using a compressional strain mechanism. And then, we propose a nonlinear model of the soft fingertip which enables us to obtain the total contact force at the contact surface of each finger in manipulating tasks. Finally, the proposed force function is verified by experiment, where a tactile sensor is used to measure the contact force distribution in the contact surface and its total force. The developed soft fingertip and its force function can be usefully applied to soft-fingered manipulations.