Abstract: To explore the biomass production response of hybrid Pennisetum to nitrogen nutrition in arid hill land in South China, the effects of four different nitrogen (N) application levels (0, 112.5, 225.0 and 337.5 kg N·ha^-1) on morpho-agronomic traits were studied. Parameters measured included yield, SPAD value, bio-energy characteristics and nitrogen utilization efficiency of P. glaucum×P. purpureum (cultivar Guinengcao-1). Application of N fertilizer promoted horizontal plant spread and shoot number, vertical growth, plant height, and stem diameter, but the fresh weight and hay yields were little changed at N fertilizer application rates above 225.0 kg N·ha^-1. Application of nitrogen fertilizer also increased the contents of cellulose and hemicellulose, calorific value and the yield of standard coal, while significantly decreasing the contents of dry matter, lignin and ash. The calorific value decreased and the yield of standard coal showed little further increase when the rate of N fertilizer application was raised beyond 337.5 kg N·ha^-1, with the result that bio-energy yield of Guinengcao-1 was also decreased. The nitrogen utilization efficiency of Guinengcao-1 did not decrease significantly with increase in N fertilization rate from 112.5 to 225.0 kg N·ha^-1, but decreased significantly at 337.5 kg N·ha^-1. Therefore, when growing Guinengcao-1 hybrid Pennisetum on arid infertile hill land in South China, N fertilizer is best applied at rates that optimize bio-energy yield. This is achieved when the N application rate is less than 225.0 kg N·ha^-1.