The present disclosure relates to a wavelength conversion device, a light source and a projection device. A light conversion region and a light path conversion region are provided on one surface of the wavelength conversion device. The light path conversion region includes a first segment and a second segment. The first segment and the second segment are configured to alternately receive excitation light and respectively guide the excitation light to different preset light paths. The light conversion region is provided with a wavelength conversion material for receiving excitation light emitted from one of the segments, converting the received excitation light into excited light that has at least one wavelength range different from a wavelength of the excitation light, and emitting the excited light.