The invention provides a method for treating and utilizing sulfonation waste acid, which comprises the following steps: firstly, collecting the waste acid generated by sulfonation in the sulfonated para-ester manufacture to a recycling pot; secondly, adding granular activated carbon inside the recycling pot to perform stirring adsorption or fixed bed adsorption; separating the waste acid solution from adsorbing agent after the adsorption, obtaining a waste acid clear solution by using a filter press to filter the waste acid, and using the waste acid clear solution for adjusting the pH value of the diazotization reaction.