Abstract: Long-term (over 20 years) fertilization experiments were conducted to study potassium (K) uptake of summer maize and potassium dynamics of fluvo-aquic soil in Zhengzhou of China. The study consisted of four treatments, CK (no fertilizer or manure), NP (nitrogen and phosphorus fertilizer applied), NPK (nitrogen, phosphorus and potassium fertilizer applied) and 1.5MNPK (nitrogen, phosphorus and potassium fertilizer and manure applied in winter wheat season, only chemical fertilizer applied in summer maize season). The results show that both in the treatments with K and without K, the dry matter accumulation amounts are constantly increased with maize growing, and the maximum values are at the maturity stage of summer maize. The K concentrations in leaves and stalks and K uptakes of summer maize are increased significantly by adding K fertilizer on the basis of applying nitrogen and phosphorus. However, by adding manure on the basis of applying nitrogen, phosphorus and potassium fertilizer (NPK), the dry matter accumulation of summer maize is not greatly affected, but the K concentrations in leaves and stalks and K uptake are increased significantly. The maximum K uptakes occur at the filling stage of summer maize in all the treatments and after that, backflow phenomenon is occurred. Compared with the soil K contents before maize seeding, the water soluble K and exchangeable K are declined or ascended slightly after the harvest, while the non-exchangeable K of fluvo-aquic soil is declined significantly. The non-exchangeable K is the main form for K uptake of maize. K uptake of summer maize has significant positive correlations with the three forms of K contents in the soil. Therefore, potassium fertilization is of far-reaching significance in improving the maize production, maintaining balance of soil potassium and realizing sustainable development of agriculture.