A field experiment with two potassium fertilizer treatments (–K and +K) was conducted to study the effects of potassium fertilizer application on oilseed rape yield under condition of potassium deficiency with focus on the different effects of potassium fertilizer application on different location of terminal raceme. The results showed that oilseed rape yield increased significantly when potassium fertilizer was applied to potassium deficiency soil, the increment was 1 321 kg/hm2 with the increase rate was 111%, pods per plant and seeds per pod increased significantly by 50.1% and 9.2% in the meantime, respectively. The potassium fertilizer improved seed weight of terminal raceme, pods per terminal raceme and seeds per pod increased by 33.6%, 21.6% and 10.3%, respectively. The enhancement of seed weight, pods and seeds per pod were different in different locations of terminal raceme, the effects of potassium fertilizer on the upper of terminal raceme was much better than the middle and lower position. Compared to the no potassium treatment, the seed weight, pods and seeds per pod in the upper of terminal raceme increased by 69.6%, 41.7% and 20.1%, respectively, and the potassium content increased by 124.4% correspondingly. All the results proved that potassium fertilizer application improved oilseed rape yield by enhancing pods and seeds per pod, and the effects of potassium fertilizer performed best in the upper of the infructescence if viewed from the yield characters of the infructescence.