Lathyrus sativus Linn. protein was extracted using the alkaline method and amino acid analysis and comprehensive assessment of nutritional value of protein were investigated. The analysis indicated that the optimized extraction yield of Lathyrus sativus Linn. protein was up to 26.1% under the condition of extraction temperature 40℃, pH 10, time 1h, and solid-liquid ratio 1∶20g/mL. The isoelectric point of Lathyrus sativus Linn. protein was pH 5 and 18 amino acids were found. The contents of glutamic acid and aspartic acid were 17.4% and 10.0%. The ratio of essential amino acids to total amino acids (EAA/TAA) was 42% and the ratio of essential amino acids to non-essential amino acids (EAA/NEAA) was 72.41% which were higher than the reference values proposed by FAO/WHO. Except for methionine + cystine, threonine, tryptophan, and valine, the contents of other amino acids were higher than WHO/FAO standard. Meanwhile, methionine+cystine and tryptophan were the first and second limiting amino acids. Moreover, the essential amino acids index (EAAI) of Lathyrus sativus Linn. protein was 1.16, which was higher than 0.9, the criteria for high-quality protein source. Thus, Lathyrus sativus Linn. proteins had high quality.