This paper reports the demonstration of a high performance 4H-SiC floating junction barrier Schottky (FJ_JBS) rectifier with a 30μm, 6×1015 cm-3-doped epitaxial layer. Extensive simulations have been performed to design, optimize and analyze the structure of the FJ_JBS rectifier. The fabricated FJ_JBS shows that breakdown voltage (BV) and differential Ron,sp are 3.4 kV, yielding the highest BV value reported for 4H-SiC FJ diodes, and 5.67 mΩ·cm2, respectively. Compared with the conventional JBS, the BV value of FJ_JBS increases by 33.3% and the Ron,sp only slightly rises by 6.2%. The corresponding Baliga figure-of-merit (BFOM) (4BV2/Ron-sp) of this FJ_JBS diode is 8.16 GW/cm2.