In the description of nonlinear response of fiber-reinforced composites, the one-parameter plasticity model developed by Sun and Chen is the simplest one, including a single parameter that indicates the material plasticity.This study focus on two methods for the determination of the model parameter.For the traditional trial and error method, a computer program is implemented to evaluate the effective stress-effective plastic strain master curve.For the second method, expression of the model parameter is derived based on the least square theory.