Litter that falls will experience decomposition involving the role of microorganisms such as bacteria and fungi. Therefore, by using adding fungi to the leaf clutter, can make the decomposition manner can be quicker. This study aims to identify the dominant species of fungi that play a role in the decomposition of Avicennia marina leaf litter. The methods used in this study are the washing method and the particle filtration method. The research shows that it does exist 15 types of fungi that predominate in accelerating the process of litter decomposition. From the identification results, the fungus belongs to the genus Penicillium sp., Aspergillus sp., Fusarium sp., Paecilomyces, and mycelia strerile. Overall, the known types of fungi belong to the Ascomycota division but belong to different families. The frequency of emergence of the fungus Aspergillus sp. was very dominating from the 15th to the 105th day of observation with a total of 59 isolates. Aspergillus sp. has a high ability to degrade lignin compounds so that it can help speed up the process of litter decomposition, of the 13 fungi found, Aspergillus sp. was the fungus with the highest occurrence frequency compared to other types of fungi.