An orientational experiment is made, using Magellen Promarx X cm GPS, in the forest in Xiaozhen District, Xinfeng County, Guangdong Province. Results are as follows: the satellite's signal receiving will be influenced by crown coverage, the GPS antenna type and the antenna height. The orientation using GPS can be carried out in Chinese fir forest. The error which GPS datum supposed TM images is less than one pixel. DGPS method can be applied to forest survey in mountainous area in South China.