Objective To study the difference in amino acid content among male flowers of different Eucommia ulmoides germplasm, and evaluate the comprehensive quality of E. ulmoides male flowers based on amino acid composition.

Method The contents and compositions of amino acids in male flowers of 193 E. ulmoides germplasm resources were determined by automatic amino acid analyzer, then the qualities based on amino acid contents were evaluated objectively by principal component analysis, and overall scores and rankings were calculated.

Result There were 17 kinds of amino acids in male flowers of 193 E. ulmoides germplasm resources. The contents of total amino acids and essential amino acids were 206.23 and 68.37 mg·g^-1 respectively, among which aspartic acid and glutamic acid were the two major amino acids. Six principal components were extracted, and the first and second principal components (factors of essential amino acids) had relatively high influence on amino acid contents in E. ulmoides male flowers. Six types of E. ulmoides germplasm with superior amino acid traits of male flowers were chosen by selecting the top 5%, and the male flowers of nine E. ulmoides germplasm resources including 10419x, 10519x, 10345x, 10444x, 10370x, 10552x, 10589x, 10339x and 10515x were evaluated as having the best quality based on their amino acid compositions.

Conclusion The principal component analysis could be used to analyze the comprehensive quality of male flowers among diverse E. ulmoides germplasm based on amino acid compositions.