Abstract: The plate-like potassium niobate（K₄Nb₆O₁₇） microcrystal with high crystallization was successfully synthesized by hydrothermal method with KOH and Nb₂O₅ as raw materials.The effects of hydrothermal temperature，reaction time，and amount-of-substance ratio of K to Nb on the crystal phase and morphology were investigated by the means of XRD and SEM etc.，and its photocatalytic activity for degradation of Rhodamine was also studied.Through the experiments，the optimum preparation conditions were obtained as follows：hydrothermal temperature was 240 ℃，hydrothermal time was 24 h，amount-of-substance ratio of K to Nb was 7，catalyst dosage was 30 mg，and reaction time was 100 min.Under such conditions， Rhodamine solution with a concentration of 20 mg/L could be rapidly degraded. 

Key words: potassium niobate, hydrothermal synthesis, photocatalytic activity