Abstract: This article attempts to screen the quantitative indices of weak light tolerance in ornamental sweetpotato cultivars. Nine physiological indices of 6 ornamental sweetpotato cultivars were tested， and the weak light tolerance of the various ornamental sweetpotato cultivars were evaluated with subordinate function analysis of fuzzy mathematics. The results showed that we can screen the ornamental sweet potato varieties rapidly and effectively with low\|light sensitivity coefficient. The six ornamental sweetpotato varieties had different tolerance to the low light. The sweetpotato showed big differences in the resilience stability under different stress. Margaret and Black Beauty were better varieties which showed higher resistance to low\|light and had resilience to stress to some degree， but the growth of Caroline Bronze was poor in low light.

Key words: ornamental sweet potato, low light tolerance, low\|light sensitivity coefficient, main factor analysis, subordinate function analysis, comprehensive evaluation