Abstract: Nitrifying and denitrifying bacteria are the microorganisms that carry out the two major nitrogen removal processes in nature. The spatial and temporal characteristics of these microorganisms in soil on Minjiang estuary wetland were studied using the method of most probable number. The count on the nitrifying bacteria was shown a decreasing trend with increasing depth on vertical distribution, whereas, that of the denitrifying bacteria the opposite. In terms of seasonal changes, both bacteria were greater in numbers in spring and autumn than in summer. The Pearson's correlation analysis showed no significant correlation between the bacterial counts and nitrogen contents (i.e., TN, NO₃^--N and NH₄⁺-N). However, the count of nitrifying bacteria significantly correlated with that of denitrifying bacteria(P < 0.01), and NO₃^--N inversely correlated with NH₄⁺-N (P < 0.05).