Abstract: To study the possible melting temperature of β-galactosidase in Kluyveromyces lactis, molecular dynamics (MD) simulations at four different temperatures (35, 50, 65 and 80 ℃) were performed for 50 ns, respectively. Then the conformational change of the enzyme and the difference of the enzyme active center were analyzed. The crucial information of temperature tolerance of β-galactosidase at the atomic level was revealed as follows: the overall conformation of β-galactosidase was the most stable at 35 ℃, which was the optimal temperature for enzyme activity; the atomic fluctuation of the enzyme increased significantly at 50 ℃, indicating that this temperature may approach the critical value of melting temperature; when the temperature was higher than 65 ℃, the structure of the protein lost its flexibility, which indicated that the protein had reached the melting temperature. Further conformational analysis showed that the microenvironment of β-D-galactopyranose (GAL) binding sites was destroyed at 80 ℃.