In this paper， the interesting phenomenon of star-burst ( which arose from the pictures taken from bulbs at night) is investigated theoretically and experimentally. Through properly simplifying the physical model of photographing process， the star-burst is analyzed theoretically depending on Francophile diffraction theory，with the influencing factors including the aperture shape，aperture size， incident wavelength and camera distance，etc. Then the influencing factors for star-burst has been systematically studied through contrast experiments. Further comparison on the results got from theoretical and experimental methods has been methodically carried out. Finally，advice for how to obtain obvious star-burst is given.