Deformable linear objects (DLOs) such as cables, hoses and wires are widely used in the real life, electric industries and medical operations. In this paper, we propose a new approach to simulate manipulating DLOs in the robotic assembly. The dynamic 2D deformation of an inextensible linear object is formulated using FEM approach. Based on the model, simulation can be efficiently implemented by matrix computation and numerical solvers for differential equations. The proposed method provides faster computation speed than methods based on differential geometry coordinate systems. Some simulation examples are illustrated to confirm the effectiveness of our methods.