Abstract: The effects of nitrogen fertilization (250 kg/ha and unfertilized) and cutting intensities (5 cm, 20 cm, or 50 cm above ground level) on the photosynthetic characteristics of Guimu No.1 (Pennisetum purpureum cv. Guimu No.1) were studied in a two factor randomized experiment. All the diurnal variations of net photosynthetic rate (Pn) in the six treatments followed a bimodal curve distribution. However, with an increase of cutting intensities, the Pn initially rose but then declined and with nitrogen fertilization, the noon break phenomenon of photosynthesis was reduced. Nitrogen fertilization increased chlorophyll content and the maximum net photosynthetic rate (Amax). With an increase of cutting intensities in the N-fertilization treatments, apparent quantum efficiency (AQE) increased, while carboxylation efficiency (CE) initially increased but finally declined; the reverse was true for the light compensation point (LCP), photorespiratory rate (Rp) and dark respiration rate (Rd). With an increase of cutting intensities in treatments with no N-fertilization, AQE, LCP, CE, Rp and Rd all declined initially but then increased. This indicated that both nitrogen fertilization and cutting intensity have some influence on the photosynthetic characteristics of Guimu No.1 with the best effect from a combination of medium-intensity cutting and 250 kg/ha nitrogen.