Abstract: Field experiment of different sowing date for potatoes, taking Ning4 and Long3 varieties, was conducted, which were planted on April 13 and 20, 2008. The relationship between the dry weight of stemleaf per plant potato every 10d in the whole growing period and meteorology factors, such as accumulated temperature, precipitation and sunshine hours, was analyzed. The results showed that the related coefficient between the dry weight of stemleaf per plant and the accumulated temperature, precipitation and sunshine hours of Ning4 no mulching sowed on April 13 was higher than Long3 (P<0.01), which indicated that the sensitivity of Ning4 was higher. The sensitivity to accumulated temperature of Ning4 no mulching sowed on April 20 was higher than Long3, the correlation of Ning4 mulching sowed on April 13 was higher than that sowed on April 20(P<0.01), which indicated that Ning4 sowed on April 13 had more sensitive to meteorological factors. Ning4 sowed on April 20, was sensitive to the accumulated temperature, and the dry weight of stemleaf per plant of Ning4 mulching increased 0.6g than that of no mulching when the accumulated temperature increased 100℃, which indicated that Ning4 mulching had more sensitive. To sum up, the optimum sowing date for Ning4 potato mulching was April 13 in Xiji County.