A distributed small signal equivalent circuit modeling method for InP high electron mobility transistor （HEMT） was presented. The distributed capacitance effect was considered in the adopted model， which is characterized by adding three distributed capacitances. For accurate modeling， the parasitic inductances are extracted first，considerig the errors introduced by the parasitic inductances when extracting the parasitic capacitance first. The validity of the proposed small signal modeling method has been verified with excellent agreement between the measured and modeled results up to 50 GHz for InP HEMT. In addition， the S-parameters’ modeling error is less than 4% in 2 ~ 50 GHz， which also proves the high accuracy of the proposed modeling method.