Based on improved charge conttrol model and combining GSW velocity-field equation, a series of analytical solutions for the static characteristics of HIGFETs such as TD-VD-VG,Gm and CG are derivel. The results of calculations are compared with experimental data reported in references, within the rang of VG2V, ID TDS, they agree very well. It is pionted out that two-lengrh model must be considered in the high field region due to greater leakage current between the gate and rhe drain. The effects of temperature on Vth, and the effects of gate length and width, temperature, GaAlAs thickness, source resistance, GaAs mobility on Gm are discussed. Possible approaches for improving performances of HIGFETs are pointed out according to the above analyses.