Abstract: The proteins from potato fruit juice were recovered by complexation with natural polyelectrolyte of carrageenan. And the free amino acids were separated and purificated through ion exchange chromatography in this study. The complex behaviors were studied by turbidity titration. Effects of p H and protein to carrageenan ratio on the yield of protein were also investigated. Free amino acids were recovered by choosing 001 × 8styrene strong cation exchange resin. Results indicated that the yield of protein reached 100% at p H3.5 and protein to carrageenan ratio of 2.5∶1(w/w). The yield of free amino acid reached 88.4%,and the dry basis content of amino acid up to 89.5%. The nitrogen materials were fully recovered in this study,which offer a certain guiding for the treatment of potato fruit juice.