In order to revisit the kinetics of amino acid transformation in the chemical evolution, a series of hydrothermal experiments has been conducted for threonine (Thr) solution. Thr transformed into glycine (Gly) and other products including peptides and polymers at 121 to 160degreesC. The Thr --> Gly decomposition rate (k(1)) is different from apparent Thr decreasing rate (k), because of the presence of other side reactions.