To develop the national standard materials of progesterone in frozen human serum and to evaluate the accuracy and standardization of serum progesterone detection kits.

Low and high concentrations of serum were from normal people and pregnant women individuals respectively，with a clear appearance，no obvious hemolysis，jaundice and lipid blood. After all tests for four infectious diseases were negative，thrombin，anhydrous calcium chloride and anhydrous sodium carbonate were added according to the proportion of 1 kU·L^-1，2.219 6 g·L^-1 and 2.65 g·L^-1 respectively，and centrifuged (4 000 r·min^-1，4 ℃，25 min) after fully mixing. After twice of multiple filtration and sterilization，serum pools were packed in ampoules to prepare candidates Ⅰ and Ⅱand stored at -70 ℃. Single factor variance method and linear regression method were used to evaluate the homogeneity and stability of the candidate. Five labs working together used reference method (isotope dilution liquid chromatography tandem mass spectrometry) to assign value for candidate. The uncertainty was calculated. At the same time，the commutability was evaluated.

Through statistical analysis, the F values of homogeneity for candidate Ⅰ and Ⅱ were 0.570 9 and 1.200 9, respectively, which were all less than F_0.05. Candidate Ⅰ and Ⅱ could be stable at least 8 h at 20-25 ℃. At 2-8 ℃, candidate Ⅰ and Ⅱ could be stable at least 33 d and 7 d respectively. Candidate Ⅰ and Ⅱ cound be stable at least 33 d at -20 ℃. Candidate Ⅰ and Ⅱ remained stable after repeated freeze-thaw cycles for 6 times. The assigned values were：candidate Ⅰ：(4.44±0.24) ng·mL^-1 (k=2), Ⅱ：(16.79±0.82) ng·mL^-1 (k=2). The determination results of candidate Ⅰ and Ⅱ were all within the 95% confidence interval of the fitting regression line established by the determination values of fresh serum samples.

Progesterone candidate had good homogeneity，stability，interoperability. It had accurate and reliable determination value，which could be used as national standard. The establishment of this national standard was of great significance for promoting the consistency and standardization of progesterone testing results.