Abstract: A multibias optimizing parameter extraction technique for high electron mobility transistor (HEMT) small signal model is described. Firstly, HEMT's small signal equivalent circuit is introduced, determining intrinsic and extrinsic elements. Secondly, a multibias decomposition based optimization method is presented. Lastly, robustness and accuracy tests, with a different set of random initial values , are performed on measured S parameters of a PHEMT device. Results indicate that the extracted parameters typically vary by less than 1%.