Knowledge of various kind of plankton are found in the digestive tract of trepang/sea cucumbers from their natural habitat is important as a reference to determine the compotition of the plankton in sea cucumber diets on the cultivation media. The aims of this study to identify the various species of plankton that are in the digetive tract of black trepang (Holothuria atra) This study was conducted in July 2016. Samples were collected from the Bama Beach, Baluran National Park. Plankton in the digestive tract of Black trepang were identified and photographed using a trinokular microscope (Nikon Eclipse E200 LED) at 100x and 400x magnification. Some species of plankton found are Pleurosigma sp., Synedra sp., Amphora sp., Oscillatoria sp., Synedra sp., Navicula sp., Nitzchia sp., Diploneis sp., and Amphiphora sp. Keywords: black trepan, Bama beach, plankton