As an effective method for extraction of succinic acid, aqueous two-phase systems based on piperidinium ionic liquids were used in this study. Effects of the alkyl chain length of cation in piperinidium ionic liquids on phase diagram and extraction efficiencies were investigated. Experimental results show that aqueous two phase systems can be formed by adding appropriate amount of piperidinium ionic liquids to aqueous K2HPO4 solutions. It can be found that the ability of piperidinium ionic liquids for phase separation followed the order [OMPip][Br]>[HMPip][Br]>[BMPip][Br]>[EMPip][Br]. The biphase-forming ability of piperidinium ionic liquids was higher than that of imidazolium and pyrrolidinium ionic liquids in the presence of K2HPO4. 75~95% of the succinic acid could be extracted into the ionic liquidrich phase in a single-step extraction. There was little difference in the extraction efficiency of succinic acid by piperidinium ionic liquids comparing to other ionic liquids such as imidazolium and pyrrolonidium ionic liquids. This aqueous two phase system by piperidinium ionic liquid is suggested to have effective application for the separation of succinic acid.