A kinematic model for a closed five-bow-shaped-bar linkage is established based on screw theory and Nominal mechanism method. Firstly, a Nominal fixed base is established using Nominal mechanism method to determine the initial configuration of the linkage. Subsequently, the exponential equations and motion screws of the joints, with respect to the initial configuration, are solved by screw theory, and then the linear velocities and angular velocities of each link are obtained directly. With the hypothesis that the barycenter of the linkage is the end effector, the kinematic equation of the barycenter is derived out and the result is consistent with the formula obtained by the D-H parameter method. Finally, based on the kinematic model of the linkage and the critical position of rolling motion, the workspace of the end effector is obtained using MATLAB, and the result is also consistent with the D-H parameter method. The mathematical derivation and software simulation demonstrate the correctness and effectiveness of the screw theory modeling method for the closed five-bow-shaped-bar linkage. As the screw theory can describe the translation and rotation motions in a unified form and avoid the problem of unclear physical meaning in D-H method, it can simplify the kinematic modeling process and make the kinematic model more concise and unified.