A color wheel phase detection method and system, and a projection device. The phase detection system comprises a color wheel (1), a color wheel motor (2) that drives the color wheel (1) to rotate, and a control circuit (3); the color wheel motor (2) is a three-phase motor, and the control circuit (3) comprises a three-phase driving circuit (31) for driving the color wheel motor (2) to operate. The phase detection system further comprises a phase detection device (4) for detecting the three-phase driving circuit (31); when detecting a preset phase, the phase detection device (4) sends a pulse signal to the control circuit (3) to implement color wheel phase detection. Therefore, the effects of low costs, high accuracy, and high reliability are achieved.