Abstract: A new catalyst for nitrogen fixation has been prepared. This catalyst may be regarded as a cluster of molybdenum and iron bonded to a poly-vinylpyridine carrier. 'The initial rate of acetylene on the new catalyst is l.3mol/mol.min and as high as the same type complex catalyst of dextrin-supported molybdenum-cysteine. This catalyst is so stable that there appears only a little decrease in activity upon repeated use. The relationship of catalystic activity with elementary composition has been tabuleted, which implies the role of the components of the nitrogenase active center. The results mentioned above are helpful for understanding the mechanism of nitrogen fixation.