Abstract: Prime farmland protection planning is both a scientific and a systemic work. Current protection planning mainly considers quantity, purpose, quality and location of the land, rarely considers the connectivity of farmlands. Large connected quality farmlands clearly have higher value for protection than small isolated ones. This paper gives a concept of connectivity of farmland, which means the connective degree of farmland with similar quality (same rank of quality, or all above a certain level of quality, or a rank span). This paper tries to figure out the distribution of better and connective farmland with connectivity concept and suggests putting this concept into the principles of prime farmland protection planning. The research of connectivity in home and abroad focuses on landscape ecology. It is a lack of research about mathematical methods from theoretical view angle, although scholars did work on the connective degree of farmland. Based on the result of farmland ranking, this paper provides three ways for measuring farmland connectivity under GIS environment: connectivity analysis, fuzzy texture analysis and quality-weighted fuzzy index. Taking Yuping County in Guizhou Province as a research field, the authors apply the way of connectivity analysis to computation and mapping the areas of prime farmland by ArcGIS, which can meet varied limits and demands. The result proves the possibility of the method. This case study shows that the method has three applied advantages: 1) Elimination of the need for arbitrarily specifying the minimum and maximum patch sizes for protection; 2) Linkage of patches which are not touching but still close in space; 3) Flexibility of user-defined quality levels.