Meal-assistance robot is a new kind of service robot. A new type of meal-assistance robot model with a few DOF, low price and high performance was presented first in the paper, in view that the existing meal-assistance robots are characterized by a large number of DOF, high price and being difficult to accept by the disabled patients in the hand who are the vulnerable groups of society, especially in developing countries. Furthermore, based on the second Lagrange's equation, the dynamics function of the meal-assistance robot was established, with the mutual force between mouth and spoon considered. Dynamics numeric simulation of the robot has been finished by using SimMechanics simulation tool, which indicates that the mutual force between mouth and spoon influences the dynamics characteristics of meal-assistance robot greatly and proved that dynamics modeling of meal-assistance robot with the mutual force between mouth and spoon considered was practical.