Dong Hy is a midland and mountainous district in the north of Thai Nguyen province, so the building of land units for evaluating the land for agricultural production in the area of the district is an urgent demand of agricultural and rural development. The establishment of the land unit mapping (LMU) bases on defining 8 scales standards, which are: land type, sloping degree, elevation, land thickness, mechanical elements of land, PHkcl land humus, total phosphorus in the investigated land for agricultural cultivation of the area. GIS technology was applied in the construction of thematic maps. The land unit map was set up by map overlay the thematic maps in GIS technology which resulted in the land of Dong Hy district consisting of 561 plots divided in to 47 LMU with a total area of 3,791,968 hectares with 67,59 hectares per each plot, in which the LMU number 37 is the biggest with 68 plots of 121,039.26 hectares, the LMU number 29 is the smallest (one plot is 3.22 hectares). The application of GIS technology in LMU forming for in land assessment is extremely necessary and highly feasible, for the agricultural production in the Dong Hy district, Thai Nguyen province.