We propose a new high speed and low power SOI(Silicon-On-Insulator) inverter circuit with dynamic threshold voltage that can operate with efficient body-bias control and free supply voltage. The performance of the proposed circuit is evaluated extensively by both the BSIM3SOI circuit simulator and the ATLAS device simulator, and then compared with other previously reported SOI circuits. The proposed circuit is shown to have excellent characteristics. At the supply voltage of 1.5V, the proposed circuit operates 27% faster than the conventional SOI circuit with almost the same power dissipation. The use of retrograde doping in the main MOSFETs can further improves the circuit performance.