Pu Luong proposed nature reserve is located in Quan Hoa and Ba Thuoc districts, in north-western Thanh Hoa province. To the north-east, the nature reserve is bordered by Mai Chau, Tan Lac and Lac Son districts, Hoa Binh province. The proposed nature reserve lies along two parallel mountain ridges, that run from north-west to south-east, and are bisected by a central valley. This valley contains several human settlements and a large area of agricultural land, and, hence, is not included within the proposed nature reserve.
The two mountain ridges in the proposed nature reserve have starkly contrasting landforms, based on their different substrates. The smaller, south-western ridge is made up of mostly igneous and metamorphic rocks, and consists of rounded forested hills and wide, shallow valleys. The larger, north-eastern ridge is composed of heavily dissected limestone karst, and is a continuation of the limestone range that runs from Cuc Phuong National Park to Son La province. Elevations in the proposed nature reserve range from 60 to 1,667 m.
The hydrology of the limestone ridge is complex, and there is little or no permanent surface water. On the south-western ridge, surface water is more common and streams are much less seasonal. However, the main drainage features of the proposed nature reserve are located in the central valley. This valley is not continuous but has a saddle at its mid-point, which forms the watershed between two small rivers. One of these rivers flows north-west along the valley, and joins the Ma river, which runs to the west and south of the proposed nature reserve. The other river flows south-east along the valley, and joins the Ma river further downstream.