The finite element method (FEM), whether the calculation is accurate or not, depends closely on object boundary condition. If the three dimensional displacement of the object obtained in experiment is regarded as its boundary condition, a new method combining the results of experiment and calculation, called combined method (CM), is formed. The combined method possess advantages of experiment and calculation. It can correct calculation and improve the accuracy of FEM. Accordingly it has more practicability. In this paper, the three dimensional displacement fields of a typical beam loaded at three points are tested by using 3 D electric speckle pattern interferometry (ESPI). Using the experimental results as boundary condition the whole three dimensional displacement fields can be calculated by FEM. The beam′s three dimensional displacement fields obtained by FEM agree very well with those obtained by experiment. This proves that the combined method is effective and practicable. The finite element method (FEM), whether the three dimensional displacement of the object obtained in experiment is viewed as its boundary condition, a new method combining the results of experiment and The combined method possess advantages of experiment and calculation. It can correct calculation and improve the accuracy of FEM. It this correct method has been more practicability. In this paper, the three dimensional displacement fields of a typical beam loaded at three points are tested by using 3 D electric speckle pattern interferometry (ESPI). Using the experimental results as boundary condition the whole three dimensional displacement fields can be calculated by FEM. The beam’s three dimensional displacement fields obtained by FEM agree very well with those obtained from experiment. This proves that the combined method is effective and practicable.