High electron mobility transistors heterostructures of AlGaN/GaN were grown by metalorganic chemical vapor deposition system on silicon carbide substrate. The growth parameters such as AlN buffer thickness, AlN spacer growth time and Al content in AlGaN barrier layer were optimized. Moreover, the effects of chamber pressure and V/III ratio at the initial growth state of GaN on film crystal quality were also investigated. The optimized AlGaN/GaN heterostructure has AlN buffer thickness of 120 nm, AlN spacer growth time of 10 s and Al content of 28% in the barrier layer. Furthermore, as a result of using higher chamber pressure and lower V/III, both the GaN crystal quality and electron mobility in the AlGaN/GaN were also significantly improved. After the growth parameter optimization, the GaN (002) and (102) planes exhibited X-ray rocking curve widths of 209 arcsec and 273 arcsec, respectively. Besides, the AlGaN/GaN structure also has an electron mobility of 1832 cm2/V-s and a sheet electron density of 1.08 ×1013 cm-2, which yielding a sheet resistance of 316 Q/sq.