The aim of this study was to determine nematode communities before and after flood in Gunja and to determine the number of nematode genera, changes in the total number of genera, trophic groups and changes in their community using MI, PPI. PPI/MI, MI2-5. Research was conducted in Gunja, 2014. on corn and the results are compared with corn a year earlier (2013.) which wasn't flooded. In research we are used four samples. Nematodes extracted from soil with bottle techniques in laboratory on Agriculture faculty in Osijek. Analyzing the samples we have confirmed the number of nematodes that are determined by gender and classified by trophic groups This research found that the total number of genera nematodes declined significantly after floods. The total number of nematodes genera was 26 before flood and after flood 18. Following genera were present in all samples in both research: Eucephalobus, Rhabditis, Acrobeloides, Cephalobus, Plectus, Panagrolaimus, Panagrobelus (bacterivors), Paratylenchus, Pratylenchus, Tylenchus, Filenchus (herbivores), Aphelenchus, Ditylenchus, Aphelenchoides (fungivors), i Eudorylaimus, Mesodorylaimus (omnivores). Trophic groups in both researches was practically the same, before flood the most common was bacterivors, than herbivores, while after the flood the most common nematodes were herbivores and then bacterivors. After flood, predators weren't found and the least were found omnivores. Predators have been found before the flood but in a small proportion (1%). The greatest statistical significance had have MI which was higher in 2014 due to the increased number of omnivores.