In order to solve the problem existing in the determination method of nitrification inhibitors and achieve effective management and control of new fertilizers，an analytical method for simultaneous determination of NBPT and DCD in fertilizers was established by high performance liquid chromatography. The results showed that the linear relationship between the mass concentration of the two inhibitors and the value of the corresponding chromatographic peak area was good in the linear range. The correlation coefficients were all greater than 0.9999. The recoveries were 91.1%-104.8% and 90.9%- 107.6%，and the relative standard deviations of 6 parallel determinations were 1.94% and 0.84%，respectively. At the same time，through the statistical analysis of an international comparison test between 18 international laboratories worldwidely，it indicated that the method not only had the advantages of simple pretreatment，good separation effect and accurate detection，but also had the advantages of wide applicability and high precision. New international standard of ISO/DIS 6650 was a good testing method which could be used world-widely.