Abstract: Scientific classification of land quality is the foundation of planning the prime farmland protection zone, and classification of farmland is one kind of farmland quality valuation method, reflecting the difference of land quality through setting farmland natural quality grade、utilization grade and economy grade. So the results can be used in the planning of prime farmland protection zone. In this paper, we take the Fangshan district in Beijing as a example, choose the farmland utilization grade as the main index, and have attempted to planning the prime farmland protection zone applying cluster analysis and GIS technology. The results show that land quality of the prime farmland is large difference in Fangshan district at present, covered from grade 7 to grade 21, and some high-grade cultivated land has been planned as general farmland. The prime farmland planned based on utilized grade covered from grade 18 to grade 21 in the plain area, from grade 10 to grade18 in the mountain area. Comparing with the situation now, the total area of the prime farmland would increase 3520.52 hm2, the prime farmland productivity could increase 44749 t according the relationship between utilized grade and standard food output. The study shows that the farmland utilization grade can be used in planning the prime farmland protection zone.