This paper discusses the result os research on the efficiency and technique of potassium fertilization in paddy soils with different water conditions and show that the potassium efficiency on these soils was in the order of gleyed paddy soil (GLP)>periodically waterlogged paddy soil (PWLP)>submergic paddy soil(SMP). The role of potassium fertilization in increasing soil redox potential percentage, decreasing soil reducing substance content, increasing the percentage of soil aerobic bacteria and decreasing the percentage of soil denitrifying bauerium and the ratio of potassium uptaken by rice from fertilizer to the total potassium uptaken were GLP>PWLP>SMP as well. Otherwise, the soil and wader temperature in rice growing season, soil potassium supplying ability and the amount of porassiun uptaken by rice from soil was SMP>PWLP>GLP.The present paper also show that the soil available K critical values of efficient application of potassium were 54, 82 and 141 mg kg^-1,respectively, SMP, PWLP, and GLP. The research also indicated the potassium fertilization rates for maximuth rice yield and optimal economic rice yield and the optimum timing of potassium fertilization on rice soils with different water conditions and different available K levels. It provided the scientific basis for rational fertilizstion of potassium.