Nowadays, the harm caused by the leakage of oil and dangerous organic solvents to the ecological environment and human health cannot be ignored, and effective treatment measures are urgently needed to alleviate the current situation. Therefore, the development of low-cost and efficient adsorbents is the key to solve the problem. In this paper, konjac glucomannan was used as flexible skeleton. Flexible aerogel based on an interpenetrating network of konjac glucomannan and reduced graphene oxide was prepared by two-step hydrothermal method. On this basis, the composite aerogel was superhydrophobically modified to improve its adsorption selectivity. A series of characterization results showed that the adsorbent had flexible three-dimensional porous structure, excellent mechanical properties, adsorption selectivity, recyclability and biodegradability. At the same time, the composite aerogel synthesized by a simple and environmentally friendly method could realize the continuous separation of oil and water by vacuum pump. It showed that its application in the field of high-efficiency oil-water separation had a broad prospect.