Gita RSD, Sudarmadji, Waluyo J. 2015. The effect of abiotic factors on the diversity and abundance of mud crab (Scylla spp.) in mangrove forests of Alas Purwo National Park, East Java. Bonorowo Wetlands 5: 11-20. The purpose of this research was to know the diversity of mud crab (Scylla spp.) In mangrove forest Block Bedul National Park Alas Purwo; know the abundance of mud crabs and to know the effect of abiotic factors on the diversity and abundance of mud crabs. This research uses a quantitative descriptive method. The diversity of mud crabs was calculated using the Shannon Wiener formula. The abundance of mud crab was calculated using the Krebs abundance formula Data analysis used simple linear regression. Data obtained from this research were the number and species of mud crab found in mangrove forest Block Bedul, National Park Alas Purwo, Banyuwangi, East Java and abiotic data, i.e., temperature, pH, salinity, substrate type, and sea tides. The results showed that the diversity index of mud crab was H '= 0.315; i.e., the level of diversity in each station is low. The abundance of mud crabs was 0.0011 ind/mÂ², i.e., the abundance in each research station is low. The result of statistical analysis showed that environmental factors had no significant effect (p> 0.05) on the diversity and abundance of mud crabs.