Abstract: The effects of potassium (K) application rates on grain yield, K accumulation and use efficiency of buckwheat were studied by fields experiments with K2O rates, 0, 22.5, 45 and 67.5 kg/ha. The cultivar of buckwheat (F. esculentum Moench)，Daliqiao was selected as experimental material. The results show that the grain yield and K accumulation are increased at the first and then gradually decreased with the increment of the K application rates, and the grain yield and K accumulation reach their maxima under the K fertilizer application rate of K2O 45 kg/ha. Simulated by a quadratic curve, the grain yields of buckwheat reach their maxima under K fertilizer application rate of K2O 46.2 kg/ha (2009) and 46.3 kg/ha (2010). The K physiology efficiency, K utilization efficiency, agronomy efficiency of K, K fertilizer physiology use efficiency, K fertilizer efficiency and K fertilizer rate of buckwheat are decreased significantly with the increment of the K application rates．In conclusion, under this field experiment conditions, the most optimal K fertilizer utilization efficiency is K2O 22.5- 45 kg/ha in Kulun town of Tongliao.