Objective · To explore the measurement uncertainties and the allowable ranges of the eight biochemical indexes, including serum Na, K, Ca, Phos, Glu, Crea, BUN, and Uric. Methods · Refer to the technical report "Medical Laboratory -Evaluation And Expression of Uncertainty in Measurement" by China National Accreditation Service for Conformity Assessment (CNAS) and Nordtest guideline, continuous accumulated data from internal quality control (IQC) and external quality assessment (EQA) of National Center for Clinical Laboratories (NCCL) were used to calculate the laboratory measurement reproducibility and offset, which were then introduced as the components of the measurement uncertainty. Based on the allowable imprecision and the allowable bias derived from the 95% CI of the measurement project, the measurement uncertainties and permissible ranges of 8 biochemical indexes were calculated and then further evaluated by the quality index models. Results · The measurement uncertainties of the 8 biochemical indexes, i.e. Na, K, Ca, Phos, Glu, Crea, BUN, and Uric, were 2.04%, 4.43%, 4.29%, 4.28%, 4.44%, 7.33%, 6.28%, and 6.25%, respectively. The allowable measurement uncertainties were 2.67%, 5.41%, 4.32%, 5.88%, 6.04%, 6.97%, 7.54%, and 7.48%, respectively. The measurement uncertainties and the permissible ranges of K, Phos, Glu, Crea, BUN, and Uric met the requirements of quality index grade 2 model and Na and Ca met the requirements of the model 3 of the quality index inder. Conclusion · The measurement uncertainties and permissible ranges of K, Phos, Glu, Crea, BUN, and Uric met the requirements of the model 2 of the quality index grade. Currently the methodology and operational techniques for Na and Ca in our laboratory can't meet the rigorous quality standards. We should communicate with the clinicians to understand their decision needs for Na and Ca. Reasonable measurement uncertainties and allowable ranges should be determined by both the laboratory and clinicians.