A field experiment under the rice-wheat rotation was conducted in Plain along the Yangtze River in Anhui. The results indicated that the yields of rice and wheat were enhanced with the increasing of potassium rate, whereas the yields decreased with excessive potassium fertilizer application. Except for the highest potassium rate treatment, potassium fertilizer efficiency of rice was also enhanced with the increase of potassium fertilizer, while there was an opposite trend for wheat compared with rice. Moreover, the difference of potassium fertilizer income exhibited a similar trend in potassium fertilizer efficiency under the rice-wheat rotation system. K absorption in aerial part increased with the improvement of potassium fertilizer rate. N and P absorption in grain for all the treatments under the rice-wheat rotation system was significantly higher than the straw whereas there was higher K absorption in straw compared with grain. With the improvement of potassium fertilizer, the absorption of straw and grain for rice and wheat exhibited a significantly increasing trend. In addition, potassium for all treatments in the farmland system showed a deficit after rice harvesting. However, the deficit was mitigated with the increasing of potassium rate. Moreover, potassium in the farmland exhibited a surplus pattern in the wheat growing season when the application rate of potassium was more than 117 kg/hm2. The potassium fertilizer efficiency showed an obvious decreasing trend with the increase of potassium rate. Therefore, it was preliminarily concluded that the application rate of potassium 156 kg/hm2 and 117 kg/hm2 for rice and wheat respectively was a prefer choice for fertilization strategy in order to guarantee high yield and maintain soil potassium fertility in the similar regions.