In this paper, a sensitivity analysis and uncertainty estimation of small‐signal model for InP HBT is presented. Analytical expressions for sensitivity are derived in terms of the measured S‐parameters based on the direct intrinsic parameters extraction. Furthermore, the uncertainties of the intrinsic parameters vs frequency are discussed to give more reliable extraction results. The optimal solutions of the parameters are obtained by utilizing sensitivity analysis. In the frequency range of 45 MHz‐40GHz, good fits between the measured and modeled S‐parameters are achieved for 5 × 5μm2 InP HBT.