Effects of rewetting of air-dried red soil on soil biota composition, nitrogen mineralization and nitrification were studied in the laboratory.Four treatments were designed: (1) rewetting of air-dried upland red soil (RU);(2) fresh upland red soil (FU);(3) rewetting of air-dried nursery red soil (RN);(4) fresh nursery red soil (FN).The results indicate: the populations of soil microorganisms including bacteria, fungi, actinomycetes in the rewetted red soil increased obviously after 5 days incubation when compared with those in the fresh red soil, especially the population of bacteria, which were 6.26 and 6.84 times as large as that in the fresh of upland and nursery soil, respectively.As a result of the increase in soil microbes, the soil microbial biomass C (SMBC) and soil microbial biomass N (SMBN) increased in the rewetted air-dried red soil treatments.The increasing population of soil microbes after 28 days.incubation leveled off and was still somewhat equal to or a bit smaller than that after 5 days's preincubation of all the treatments.However, the population of microbes in the rewetted air-dried red soil was still larger than that in the fresh red soil after 28 days.incubat ion.With the increase in microbe population and biomass, nitrogen mineralization was sped up, which led to increase in NH₄⁺-N concentration.After 28 days.incubation, the NH₄⁺-N concentrations in the rewetted ai-rdried soils increased in comparison with those after 5 days.preincubation and obviously higher than in the fresh soils.At the same time, NO₃^--N concentrations also increased, but they were significantly higher in the fresh soils than in the rewetted red soil.The experiment also shows that after 28 days.incubation, the population of freeliving nematodes in the treatments of rewett ing air-dried upland and nursery red soil of could hardly recover, being 16.0% and 30.1% of that in the fresh red soil, respectively.After 28 days.incubation of the rewetted air-dried red soil, the net mineralization and mineralization rate increased significantly (p < 0.05), but the net nitrification and the net nitrification rate decreased significantly (p < 0.05), when compared with that in the fresh red soil.The possible reason was that the populations of ammonium oxidi-zers and nitrite oxidizers, which play a key role in the process of nitrification, could hardly get recovered from the damage of air-drying.