Abstract: In order to regulate the potassium application rate of spring-sowing potato in southern Fujian, six potassium application rates of 0(A₁, CK), 75(A₂), 150(A₃), 225(A₄), 300(A₅) and 375 kg·hm^-2 (A₆) were set to study the effects of potassium application rate on the growth, yield and quality of the spring-sowing potato Quanyun No.4 in southern Fujian through the field experiment. The results showed that the application of potassium fertilizer could increase the SPAD value and leaf area of potato, and was beneficial to the formation of carbohydrates under the condition of spring sowing in the yellow-red soil of southern Fujian. The potato treated with the high potassium application rate of A5(K₂O 300 kg·hm^-2) had the best yield increase and income increase. Compared with no fertilization (CK), the contents of crude protein and reducing sugar in potato tuber treated with the high potassium application rate above the level of A₄(K₂O 225 kg·hm^-2) increased significantly, and the starch content of them treated with the medium potassium application rate above the level of A₃(K₂O 150 kg·hm^-2) were significantly increased, while the content of vitamin C was decreased with the increase of potassium application rate. Under the experimental conditions, the suitable K₂O application amount for the spring-sowing potato Quanyun No.4 in southern Fujian was 225-300 kg·hm^-2.