In order to study mirror flexible lens seat’s flexibility，the flexibility matrix of flexible lens seat is established by the adjoint transformation，the obtained axial and lateral flexibilities are 9.58×10-8m/N and 1.38×10-8m/N respectively，and the simulated axial and lateral flexibilities are 1.00×10-8m/N and 1.33×10-8m/N by using the finite element analysis software ANSYS.Assuming the flexibility matrix that locate between lens seat and simulation is 6×6 diagonal matrix，the matrix combination is applied to a mirror seat theory model，the expression of lateral flexibility about diagonal elements is gotten.The experimental data of lateral flexibility is nonlinear fitted，and its values are gotten，and the calculated axial and lateral flexibilities are 4.039×10-7m/N and 2.20×10-7m/N respectively.The difference between the analyzing results and the measured values are 9% and 2%.The flexibility experimental data is nonlinear fitted by using the optimized method，and the method avoids the physical properties such as anisotropy.The flexibility model is established directly in the mathematical model，and it provides a reference for solving the similar problems in project.