The effect of application sequence and ratio of ammonium and potassium on rape growth and nutrient uptake was studied through rape pot experiment. The results showed that when the mol ratio of NH4+/K+ applied was 1:1, the growth and nutrient uptake of rape were reduced greatly in the treatment with potassium applied after ammonium, which could be attributed to the fixation of ammonium promoted by the later application of potassium. While the mass ratio of K+/NH4+ (about 3:1 in mol ratio), less influence of ammonium and potassium interaction was observed on plant growth and nutrient uptake. The results also showed the importance of proper ratio of N/K for the normal growth of plants.