With analysis on internal carrier transport mechanism in silicon carbide(SiC),an improved analytical model for dc current voltage and small signal parameters of 4H-SiC metal-semiconductor field effect transistor(MESFET) is proposed considering carrier velocity saturation and charge controlling.Incomplete dopant ionization and parasitic drain-source resistances are considered simultaneously.The simulated maximum transconductance is 48 mS·mm^-1 at a gate voltage of 0 V.Simulations and physical measurements show good agreement.The model is simple in calculation and distinct in physical mechanism.It is suitable for design and research of SiC devices and circuits.