The deformations of the 600mm aperture interferometer mirrors induced by gravity and supporting forces must be controlled strictly to ensure the accuracy of the large aperture interferometer to achieve 63nm. The mirror deformations induced by two types of forces and four axial distribution positions are analyzed respectively by finite element method. And the deformed interference wavefront are simulated by synthesizing deformations of reference flat and test flat mirrors. The maximum deformed interference wavefront formed by the cosine wave force at the middle of the mirrors and the minimum formed by the square wave force at the periphery of the mirrors. The peak to valley value varies 30nm and root mean square value varies 2.8nm between them. The measurement accuracy of large aperture interferometers can be improved by adjusting the force distributions and supporting positions of the mirrors according to the analysis.