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Monitoring the frequency changes of hard and non-degradable Ostracod shells can provide valuable information about the past conditions of inland wetlands sediments as a biological index. In this regard, a sediment core with a length of 38 cm was harvested using a static sediment core sampler at the beginning of the delta of Gavkhooni international wetland (Shakh-Kenar station) in April 2019, and the number of Ostracod shells were counted in five groups of particle size simultaneously with determining the physical characteristics of sediments (particle size distribution, density, and moisture content). The results show that there is a significant negative correlation coefficient (r=-0. 686 to-0. 477) between the density of the dominant size groups of Ostracod s with the percentage of gravel and sand. Also, the results show a significant positive correlation coefficient (r= 0. 579 to 0. 638) between the density of these groups with the amount of silt and clay. Based on to the negative correlation of Ostracod s with coarse particles, it can be inferred that high-energy environmental conditions such as seasonal floods and massive floods during the wet season have potentially reduced the density of Ostracod s in this region. While the disruption of the natural hydraulic regime of the Zayandehrud River and the lack of heavy floods in the river delta in the last three decades have reduced the environmental energy of the delta and increased the percentage of silt and clay particles, and the density of Ostracod s.