A pot experiment was conducted in order to study the effects of different forms of potassium fertilizer on the biomass of three successive crops (oilseed rape, oilseed rape, and rice), potassium uptake, potassium balance and potassium content of soil. The results indicated that there were the same results between the treatments of citrate-soluble and water-soluble potassium fertilizer compare with K0 treatment (no potassium fertilizer). They significantly increased the biomass of three crops. The total potassium accumulation amount of three crops increased by 155% compared with K0 treatment. The ratio of potassium balance was 0.79. They could ease the potassium deficit of soil which will contribute to maintain soil potassium balance. However, the treatment of comminuted potassium ores had not significantly effect on the increment of biomass and potassium accumulation amount compared with K0 treatment. The potassium existed in the comminuted potassium ores was difficult to be absorbed by crops. The treatments of citrate-soluble and water-soluble potassium fertilizer had higher soil available K and slowly available K than the others after the first season harvest. Whereas, the differences among the treatments became smaller with three seasons harvest. Therefore, citrate-soluble potassium fertilizer which had the same effect compared with water-soluble potassium fertilizer, can be supplied into soil, increase crop biomass, ease the consumption of potassium and sustain soil potassium balance.