An anti-fouling aerogel with superior separation performance for separation of oil/water emulsion is of great significance to industrial development due to continuously increasing oily industrial wastewater. Herein, a superhydrophilic/ underwater superoleophobic porous biobased aerogel with a three-dimensional network structure was prepared by the agricultural waste corn stalk (CS) incorporated with konjac glucomannan (KGM) through simple sol-gel and freeze-drying methods. The oil/water separation mechanisms and the effect of aerogel structural changes on the separation performance of CS/KGM aerogel for oil-in-water emulsions are discussed in detail. Using toluene as an oil phase, CS3.50K1.25 exhibited outstanding separation performance with an excellent separation efficiency above 96.26% and a high permeate flux above 2,381 L m-2 h-1 for oil-in-water emulsions. As expected, the separation efficiency and permeation flux can be wholly recovered after washing, indicating the aerogel possesses good sustainability. Moreover, CS/KGM aerogel has the advantages of low cost, simple preparation, eco-friendly and anti-fouling, revealing a promising candidate for the treatment of oily wastewater pollution.