The original calibration curve for determination of target element is usually configured in spark discharge atomic emission spectrometer when delivery. After standardization and curve confirmation, the testing can be performed by the user of instrument. The accuracy of original calibration curve in spectrometer will directly influence on the accuracy of determination results. The determination values of low content Fe in nickel based alloy were negative sometimes and the precision was bad when the spectrometer in our laboratory was used. The accurate results could not be obtained even the control sample was adopted. In order to meet the requirements of product standard, the downward continuation of lower determination limit for Fe in nickel based alloy was conducted to improve the analytical accuracy of Fe. The interference correction mode and correction coefficient of Mo for calibration curve of low content Fe were adjusted in experiments, thus solving the problem that the determination values of low content Fe might be negative. The new control sample was added into calibration curve. Moreover, the original cubic curve for calibration curve was refitted and changed to quadratic curve, which greatly enhanced the precision and correctness of determination results. Consequently, a new calibration curve for the determination of low content Fe in nickel based alloy was established. The lower determination limit of Fe was extended from 0.50% (mass fraction) to 0.010% (mass fraction).