In this study, polyacrylicacid precipitation alkalescence protein from Momordica charantia L. seeds was studied, and the effect of conditions on experiment was also evaluated. Isoelectric precipitation is achieved by adjusting the pH of a protein solution and is based on that a protein's solubility is at minimum at its pI. The sample was titrated to pH 6.0 with citric acid, and 14.62% proteins were precipitated. With hydrochloric acid to pH 4.0, 32.49% proteins were precipitated. With the acetic acid to pH 6.0 and pH 4.0, 26.17% and 38.72% proteins were precipitated, respectively. In the 1 mL Bitter melon seeds extraction(pH 4.0) adjusted by acetic acid, hydrochloric acid and citric acid, the optimum dosage of PAA (1%) precipiting alkalescency protein (pl 8.65-9.30) was 100 microL, 120 microL and 100 microL, respectively. The respective extraction (1mL) was titrated to pH 5.0, pH 4.0, and pH 3.0 by acetic acid. After isoelectric precipitation, the PAA precipitation protein was performed. When concentration of PAA (1%) was 160 microL/mL, the protein decreased in the supernatant was 33.77% at pH 5.0, and 43.56% at pH 3.0. When concentration of PAA (1%) was 120 microL/mL, the protein decreased in the supernatant was 30.83% at pH 4.0. PAA-Protein complex could redissolve in alkaline conditions (pH > 9.0) and the protein most easilly redissolved when the NaCL was 3.0%. The bitter melon seeds extraction after PAA purification flowed through the Sephadex G-75 columns. The peaks I and II were obtained after 175 min and 300 min, respectively. SDS-PAGE and IEF analysis showed that the molecule weight from peaks I was 30 kD with pI 9.5, peaks II 10 kD with pI 9.3.