This paper deals with the effect of clay minneral (montmcrillonite) on the mineralization of nitrogen in proptein (gelation). The results obtained showed that (1) different states in which protein and clay mineral remained could lead to different mineralization percentages of nitrogen in protein in the order: complex < mixture < pure protein; (2) the more the protein-nitrogen in complex or mixture, the more the nitrogen mineralization, but the reverse was true for pure protein; (3) the mineralization percentage of nitrogen in protein was less in soil medium than in quartz sand meditun no matter what state it existed, showing that soil might proptect prorein nitrogen from degradation by microorganisms, and this protection varied with different soils wing to the different clay minerals in different ce soils.