Winter diet composition, selectivity and foraging strategy of red deer (Cervus elaphus alxaicus) was studied with a microhistological analysis technique, using faeces and food in the stomach in combination with field investigations from November 2003 to February 2004 in Helan Mountains between Ningxia Muslem Municipality and Inner Mongolia Municipality. We collected 219 faeces pellets from red deer,which formed 14 composite samples. The results showed that Ulmus pumila, Populus davidiana, Prunus monglica, Dasiphora spp., Graminoids (Stipa spp., Poa spp.) and Caragana spp. were staples of the red deer. The percentages of the above items in the diet were 27.37%, 11.75%, 9.83%, 8.12%, 7.51% and 6.52% respectively. The red deer had positive selectivity for Ulmus pumila, Populus davidiana, Prunus monglica, Dasiphora spp., Caragana spp. and Juniperus rigida, and negative selectivity for Graminoids (Stipa spp., Poa spp.), Pinus tabulaeformis and Pinus crassifolia. Their preference order was as follows: Populus davidiana＞Juniperus rigida＞Caragana spp. ＞Prunus monglica＞Dasiphora spp. ＞Ulmus pumila＞Graminoids＞Pinus tabulaeformis＞Pinus crassifolia. The results of spearman correlative analysis has show that the food selectivities of red deer did not correlate with water, crude ashes, crude protein, crude fat, crude fibre and nitrogen-free extract. The crude protein percentage in the nutritional composition of browsed plants, was sufficient for the red deer, but energy expenditure may be a more critical factor for the wintering red deer. To obtain maximum energy input with minimum energy output is the foraging strategy of the red deer in winter.