The intrinsic elements are described as functions of the extrinsic parameters.Those relative errors of intrinsic elements are proposed as objective functions.Extrinsic element values of FET's at unbiased state are used as the initial values of the independent variables.Then the intrinsic element values of ‘hot’ FET's are extracted with the optimization method.The results show that the relative errors of S-parameters are 0.09% for S₁₁,1.1% for S₁₂,0.08% for S₂₁,2.26% for S₂₂,respectively.The key properties of the method are fast convergence,high precision and efficiency.It is easy to transplant the optimization method into microwave CAD tools for circuit design and simulation.