Using the single variable laboratory experiment, the wetland sediment in tidal flats areas of Min river estuary were collected to research the effect of pH on the nitrification, denitrification and mineralization processes of the nitrogen (the pH conditions were setting at 2.5, 3.5, 4.5, 5.5, 6.5, respectively). The results suggested that: In the nitrification process, lower pH (the pH was 2.5) showed the obvious inhibition on the nitrification activity, however, at other pH conditions, the influence on the nitrification rate of the sediment varied little. Which indicated that the number and the activity of the nitrifying bacteria were typical limited under the strong acid surrounding. In the denitrification process, the denitrification rate of the sediment decreased with time but the denitrification activity increased. Besides, the strong acid condition (the pH was 2.5) in some degree had inhibitory effect on the denitrification activity. Results indicated that denitrifying bacteria in the sediment was not active or the acid resistance bacteria was rare under strong acid condition. Finally, mineralization of the nitrogen was researched and no universal?rule was found between the pH and the mineralization rate, which showed that the pH had no direct effect on the mineralization process of sediment in the wetland.