Abstract: Given that the catalytic mechanism of γ-glutamylamine synthetase in synthesizing L-theanine from L-glutamic acid and ethylamine remains unclear， molecular dynamics simulations were performed through docking γ-glutamylamine synthetase with substrate molecules such as glutamic acid and ethylamine. The binding modes of γ-glutamylamine synthetase to the substrates ATP， glutamic acid， and ethylamine were analyzed. Additionally， the mechanism of γ-glutamylamine synthetase in catalyzing the synthesis of L-theanine was explored， further refining the catalytic mechanism of this enzyme. This research endeavor establishes a fundamental basis for the construction of engineered strains that produce high yields of L-theanine.