The content of nickel oxide in neodymium oxide was determined by ICP-OES method. The content of nickel oxide was 0.002 7%. Various influencing factors in the detection process were analyzed. The reliability of the measurement results was expressed by relative expansion uncertainty (U_rel=12%, k=2). The calculation of re-lative uncertainty component shows that the relative uncertainty component introduced by standard curve fitting is the largest, u_rel(c₂)=5.639%, followed by the relative uncertainty component introduced by the preparation of standard solution, u_rel(c₁)=0.879%. This paper can provide a reference of the result uncertainty analysis for relevant testing personnel.