Scientifically established strategy of nature protection is one of the most important directions of modern science. Phong Nha - Ke Bang, largest national park of Vietnam plays world-important role in conservation of unique nature and global genetic diversity. Investigation of forests allied to western border of the national park funded by Kreditnstalt fur Wiederaufbau - German Development Bank was realized during summer 2011. Current monograph presents main results of these studies including description of vegetation and data on inventory of local floras in area proposed for extension of the protected territory. Obtained data presented in this monograph indicate straight advisability of expansion of national park on territories with intact primary forests having full spectrum of habitats and living forms of indigenous nature of Indochinese Peninsula. This area also will play role of significant biodiversity flow corridor between protected areas of Vietnam and Laos. If protected areas of both countries were to be connected by explored and studied area, the combined reserve would be the largest surviving karst primary forest in south-east Asia.