An environment-friendly flocculant and application thereof belong to the technical field of environment-friendly flocculants. At present, the most widely applied flocculants are mainly inorganic flocculants (such as 
polyaluminum chloride) and synthetic organic flocculants (such as 
polyacrylamide), the flocculants have certain 
toxicity and are difficult to degrade, secondary 
pollution can be caused when the flocculants are widely used, and waste residues cannot be treated. The invention provides an environment-friendly flocculating agent which is non-toxic, harmless, free of secondary 
pollution and good in performance and application of the environment-friendly flocculating agent. The main component of the environment-friendly flocculating agent is a 
dextran-
citric acid anionic 
polymer. The preparation method comprises the following steps of: adjusting the pH value of a 
citric acid solution to 7-9 by using 
sodium hydroxide, well mixing and stirring the 
citric acid solution with a 
dextran solution, adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide 
hydrochloride, and reacting for 12-36 hours, the 
molar ratio of edc to citric acid being (1-2): 1; and adding 
ethanol for 
precipitation, and washing and 
drying the precipitate to obtain the flocculant. 
Soybean meal waste liquid can be used for 
livestock breeding after being flocculated, the preparation is simple, and the efficiency is high.