Alkali lignin from wheat straw pulping was purified with organic solvents. Effects of different solvents and solvent dosages on yield and composition of purified lignin were investigated. The suitable solvent system and purifying conditions were determined. The results indicated: the ideal solvent system was a mixture of acetone and water (1∶1,v/v), the solvent to lignin ratio is 10∶1. Under this condition, the yield of lignin was 92.24%, the content of lignin is increased from 26.12% to 41.54%, the content of total sugar and ash in purified lignin were decreased from 16.14% to 3.43% and 34.29% to 27.12% respectively.