For the analysis on climate potential in the province of Phu Tho to expand the cultivated area of Doan Hung grapefruit, with the help of statistical probability, establish an equation to relationship between climate and productivity of grapefruit Doan Hung district. From this equation, substitute the climate data Phu Tho province received theoretical product grapefruit of different areas in the province of Phu Tho. North - East of province of Phu Tho has afavorable climate conditions for the development of Doan Hung grapefruit, South - West of the province of Phu Tho hasn't a favorable climate conditions for the development of Doan Hung grapefruit.