Background and Objectives: For total analytical error, imprecision (SD) and bias, performance goals for laboratory tests have most often been developed. A total analytical error goal requires that the combination of errors from all sources (random and systematic errors) be within some acceptable limit. Materials and Methods: Fifty vials of sodium and potassium standards (Sandos Company) were chosen. Then, the concentration of sodium and potassium in these standards were daily measured using flame photometry for 50 days at biochemistry laboratory (Ghaem hospital, Mashhad). Thereafter, the mean, standard deviation, random and systematic analytical errors, and total analytical error from these values were calculated. Results: The systematic and random analytical errors for standard specimens using flame photometry method for sodium and potassium are με (Na) = 0.36, με (k) = 0.012, σε (Na) = 0.69 and σε (k) = 0.11 respectively. Meanwhile, the total analytical error of flame photometry for measurement of sodium and potassium was 1.74 mM/l and 0.232 mM/l respectively. Conclusion: In this study, it was found out that flame photometry system has good precision and accuracy and its total analytical error for measuring of sodium and potassium are within the acceptable range.