In this study, adsorption of different dibasic acids was performed on Onion peel carbon, Onion peel as an adsorbent, is low cost, we have simply used the criteria of low cost as well as eco-friendly adsorbents. It has proven to be significantly effective with the provision of satisfactory adsorption capacities for the removal of pollutants from waste water. We have studied adsorption on different monobasic and dibasic acid by taking onion peel as an adsorbent. the dibasic acids under study were oxalic acid, Malonic acid, Succinic acid and Glutaric acid. n. The results obtained when compared with different acids the conclusion obtained was Comparison of difference between dibasic acids (oxalic acid, malonic acid, succinic acid, glutaric acid).From the readings obtained it is observed that extent of glutaric acid is greater than succinic acid, succinic acid is greater than malonic acid, and malonic acid is greater than oxalic acid.i.e., glutaric acid > succinic acid > malonic acid > oxalic acid.The reason behind the above conclusion must be the presence of 3 CH2 group in glutaric acid, and absence of 1 CH2 group in succinic acid, or 2 CH2 group in malonic acids, or 3 CH2 group in oxalic acid.