Abstract: To provide theoretical basis of the optimal row and plant spacing for high yield and quality of potato under certain planting density，in this study，four and seven ratio of row spacing to plant spacing were applied under two planting densities of 3.75 × 104 and 6 × 104 plants · hm-2，respectively，to identify the effect of widening row spacing and shortening plant spacing，which is to increase the ratio of row spacing to plant spacing，on dry matter weight，light distribution，photosynthetic characteristics，chlorophyll fluorescence characteristics，yield and starch，protein，vitamin C，reducing sugar content in potato cultivar Qingshu 9. The results showed that dry matter weight of stems and leaves，leaf area index，chlorophyll content，Pn，Tr，Gs，Fv/Fm，PSⅡ，qP，yield and content of starch，vitamin C，and soluble protein were significantly or extremely significantly increased under the low ratio of 1.5 or high ratio of 2.5 of row spacing to plant spacing，but Ci，NPQ and reducing sugar content exhibited opposite tendency. The optimal row spacing and plant spacing for potato cultivar Qingshu 9 to obtain high yield and good quality under the planting density of 3.75 × 104 and 6 × 104 plants · hm-2，were 63.3 cm/ 42.2 cm and 64.6 cm/25.8 cm，respectively.

Key words: potato, the ratio of row spacing to plant spacing, photosynthetic performance, yield, quality