In this paper, a 1 MHz LLC half bridge resonant converter with GaN Enhancement mode HEMT (GaN E-HEMT) is implemented. The power density of the power converter is improved with higher switching frequency and achieve higher efficiency with soft switching technique. The operating principle of half bridge LLC resonant converter is discussed and the characteristics and gate driver circuit requirements of the wide bandgap devices are studied. Finally, the digital signal processor, TMS320F28035, is used to realize the laboratory prototype with the input voltage 400 V, the output voltage 12 V, and rated output power 240W. The synchronous rectifier is used on the secondary side to reduce conduction loss to improve efficiency. The experimental results show that efficiency can be as high as 94.1% at 50% load and 92.1% at full load.