This paper studied the effect of light sources on photosynthetic efficiency. The photosynthetic photon flux was calculated from the spectral photon flux data by integrating the photon flux and yield photon flux was determined as the product of the spectral photon flux and the relative quantum efficiency over the 300 and 800 nm, which was varied depending on the light sources. When comparing the values of yield photon flux among artificial lamps, high-pressure sodium lamp was higher followed by metal halide, fluorescent, and incandescent lamps. When chrysanthemum (Dendranthema grandiflora Tzvelev) cv. Puma was grown under different artificial light sources, photosynthesis and leaf chlorophyll contents (SPAD values) were in the same order where high-pressure sodium lamp were highest and incandescent lamp least. High-pressure sodium lamp was the best supplemental light source because it provided more photosynthetic active light (197.9 μmol·m-2·s-1), more yield photon flux (188.7 μmol·m-2·s-1), and higher photosynthetic efficiency (0.87) than others.