This study aims to determine fish's diversity, abundance, and dominance in Ulak Lia Lake, Sekayu District. This research was conducted at Lake Ulak Lia, Sekayu District, Musi Banyuasin Regency, from February to March 2021. The fish sampling method was performed by direct catching at three predetermined observation stations using nets. Netting was carried out for 12 hours, taking catches with traps that have been installed in the morning from 7 a.m. to 9 a.m., depending on conditions or weather. Sampling was marked using a bamboo buffer and the help of the Global Positioning System (GPS). The results showed that the Diversity Index ranged from 1.85 to 1.91 indicating low diversity. The fish abundance index ranged from 30.16 to 36.87 indicating low fish abundance. Where the Dominance Index 0.71-0.72 shows a moderate dominance index. Meanwhile, the dominant fish in Ulak Lia Lake is the Sapil fish (Helostoma temminckii).