Abstract:Cymbidium sinense(Anar)Willd. plants were cultured hydloponically in culture solution at different K levels following K starvation. The contents of Carbohydrate and protein as well as some enzymes activities in various growth periods had been measured. With increasing K concentration, the contents of soluble suber, starch, cellulose and protein in plants treated with 5 mrnol/L KC1 were inerased by 125, 117, 127 and 41% respectively than those of the control. However, these KC1 treated plants had reduced by 44 and 24% in the contents of reducing sugar and free amino acid respectively than those in the control. Pseudocorm was the major organ for storing reducing sugar, soluble sugar, starch,protein and free amino acid, but cellulose mainly diStributed in leaf. When K was sufficient to plant requirement, the activity of pyruvate kinase in leaf iucreased by 15 times as against the control, and nitrate reductase was also about 1. 8 times the activity of the control. The possible reason for K promoting growth, development and disease resistance in C. sinense was discussed. And, three methods of Preliminary physiological diagnosis for K nutrition in this Plant were also suggested.