Abstract: The thermostability and specific activity of lipoxygenase(Ana-LOX) from Anabaena sp. PCC 7120 were improved with replacing valine with alanine by site-directed mutagenesis. Compared to the wild-type enzyme which had a half-life(T1/2) of inactivation of 3.8 min at 50 ℃,the T1/2of mutant enzymes with V421 A and V40 A substitution increased to 4.4 and 7.0 min,respectively. The double mutant V421A/V40 A showed a synergistic effect with a T1/2value of 8.3 min,resulting in a 1.18-fold improvement compared to the original Ana-LOX.V421 A,V40A and V421A/V40 A also obtained 4.83%,41.58% and 80.07% increase in specific activity,respectively.And,the mutant enzymes obtained 5℃ increase in optimum temperature than the wild-type enzyme(35℃).This study provided useful theoretical reference for enzyme molecular modification and application in vitro.