In this study we aim to determine the effects of potassium on nitrogen (N), phosphorus (P) and potassium (K) uptake and utilization at the late growth stages of muskmelon with 6 K levels, namely K1-K6 (0, 3, 6, 9, 12, 15 mmol/L). The results showed that K application could decrease N concentration in the organs of muskmelon, decrease N concentration in the root and stem and leaves at the ripening stage, significantly increase N accumulation in fruit; K application could improve P concentration in the root and fruit and P accumulation in the all organs of muskmelon, significantly increase P accumulation in the fruit and plant; K application could increase K concentration and NPK accumulation in the organs of muskmelon, significantly promote K accumulation in the stem and leaves, fruit and single plant; K application could significantly improve N physiological use efficiency and P harvest index, increase N harvest index, decrease significantly K harvest index and P, K physiological use efficiency. Treatments of K2, K3 and K4 had the higher single fruit weight, but the difference was not significant. The significantly correlation between K levels and N, P, K concentration in the muskmelon were correlated with different organs and stage. K levels were significantly negatively correlated with N concentration and positively correlated K concentration. N harvest index were no significantly correlated with N, P, K concentration in the organs, but significantly negatively correlated with N accumulation of stem and leaves; P harvest index were significantly negatively correlated with N accumulation of stem and leaves, but significantly positively correlated with P, K concentration and accumulation in fruit; K harvest index were extremely significantly positively correlated with N concentration in the root and fruit, significantly negatively correlated with P concentration in the root, extremely significantly negatively correlated with K concentration and accumulation in the stem and leaves and fruit. After comparing the goodness of fit (the determination coefficient R 2), it’s better to use a quadratic polynomial for the fitting K levels and P concentration of stem and leaves at the ripening stage, a linear for the fitting K levels and K concentration of root at the ripening stage, a three-parameter exponential or a five-parameter two-exponential for the fitting K levels and K concentration of root at the ripening stage. Comparing nutrient absorption and utilization in the three treatments, the K levels for 9 mmol/L (K4) had good N, P, K physiological utilization efficiency, K4 was conducive to K nutrient uptake and maximized economic benefit.