This present study to determine the potential of Neptunia oleracea as a phytoremediation agent for petroleum liquid waste in terms of various parameters such as physical temperature, and chemical parameters, namely pH, sulfide, and ammonia. Crude oil liquid waste is a hazardous waste if discharged directly into the environment, especially water. In this research, a method of biological treatment of petroleum liquid waste was used by utilizing aquatic plants, namely Neptunia oleraceae. Phytoremediation is a way to treat waste that still contains contaminants thus levels can be minimized and even accumulated by various types of plants. This phytoremediation technique uses a simple bioreactor with various concentrations of petroleum liquid waste, namely control (0% waste), 10% waste, 20% waste, and 30% waste. The results of this study can be seen that the Neptunia oleracea plant is able to survive in petroleum liquid waste with a treatment time of approximately 3 weeks. In testing the levels of ammonia and sulfide after treatment showed fluctuating results from week to week. This is a response from Neptunia oleracea which uses these compounds in its metabolic processes. The ability of Neptunia oleracea to reduce sulfide and ammonia levels indicates that this plant can be used as a phytoremediation agent for petroleum liquid waste.