Functionally graded materials are widely used in aerospace thermal structures. In order to solve the technical difficulty of simulating special mechanical behavior caused by the heterogeneous characteristics of functionally graded materials， based on the finite element method framework， the plane 4-node and 8-node isoparametric gradient elements are developed through reforming the element stiffness matrix of which the material gradient is introduced into the shape function. And the simulation technique for functionally graded material structure is established on the basis of the ABAQUS platform， where an isoparametric gradient element UEL （User-defined element） sub-routine is developed using Gaussian integral numerical method. First， a square plate of functionally graded material is used to study the influence of the mesh density on the simulated results， and the convergence of the plane 4-node and 8-node isoparametric gradient elements is verified. Then， a comparative analysis of simualtion accuracies of the gradient element and the conventional element is carried out. When subjected to complex load conditions， the stress field calculated by the conventional element appears to be stepped and achieves low fidelity， whereas the stress field obtained by the gradient element is smooth and continuous. The gradient element requires less number of element to obtain more accurate simulation results than the conventional element. In the end， the simulation of the functionally graded material perforated structure and cantilever is carried out. The number of gradient element required to obtain convergent results is far less than that of the conventional element. This work reveals that the simulation accuracy and efficiency of the plane 4-node and 8-node isoparametric gradient elements is higher than that of the plane 8-node conventional element， and even far higher than that of the plane 4-node conventional element.