The behavior of very high cycle fatigue in automotive alloy wheels have become a critical issue for safety, due to their prolonged service life. For the test, a specially designed, dedicated ultrasonic fatigue test (UFT)system was utilized to investigate the high cycle fatigue behavior of A356-T6 aluminium alloys. The hourglass-shaped specimens were specifically designed according to the alloy``s dynamic elastic modulus and fatigue-tested up to 109 cycles at room temperature under completely reversed loading conditions of R=-1. SN curve was plotted, showing monotonic decrease in the test range. Cracked area and fracture surface after tests were investigated using a scanning electron microscope(SEM). It was shown that cracks were initiated from a surface flaw and then propagated into the internal area. Fracture surfaces consist of mostly dimples, typically as in other ductile fracture mode. This test method can be an alternative test methods, since it shows several merits over conventional fatigue testing methods such as fast test speed and effectiveness.