Potassium is one of the three most important plant nutrient elements,so many researchers pay attention on its fertilizer efficiency.But fertilizers were all industrial products containing many other nutrient elements in most experiments of fertilizer efficiency.All the other nutrient elements,including necessitous elements and beneficial elements in potassium fertilizer (KCl) were analyzed by method of ICP-MS.The results showed that KCl fertilizer contained many necessitous elements (Mg,Ca,Mn,Fe,Ni,Cu,Zn and Mo),the concentrations of them are 50.51,1 309.48,5.44,500.83 μg·g-1 and 65.54,238..85,212.44,10.40 ng·g-1 respectively;beneficial elements (Na,Al,Si,Co and Se) are 25 095.89,3.83,3.40 μg·g-1 and 13.12,23.25 ng·g-1 respectively.All the above elements could influence the results of potassium fertilizer efficiency experiments,so pure fertilizer should be used in the future potassium fertilizer efficiency experiments.