///In this paper, the 100Mo/97Mo ratios of Fisher-Mo standard solution and double spike were calibrated by 104Pd/102Pd firstly, and then the calibrated 100Mo/97Mo ratio was employed for calibration of other Mo isotopic ratios. The external precision achieved over a period of 10 months is 0.035‰/amu at 95% confidence level, better than that of sample-standard bracketing. There is no difference in the Mo isotopic composition calculated by different calibration results, which indicates that the effect of different spans of time and instruments and the precision of 104Pd/102Pd can be neglected. The Mo isotopic compositions of 2 black shale samples obtained in this laboratory is in agreement with that of the open university of UK, showing that the Mo isotopic data of the authors’ laboratory are reliable.