Abstract: Microgravity environment in space affects organism. The biological effects of microgravity have been used a clinostat to simulate. The clinostat treatment induced the increase of gibberellins （GAs） and the activity of total amylase （especially the increment of a-amylase activity）, as well as the degradation of starch grains in carrot callus cells. The increment trend of GAs and α-amylase activity was con-sistent. Further more, ancymidol, the inhibitor of the biosynthesis of GAs could remarkably repress the increment of α-amylase activity induced by the clinostat treatment. Therefore, we deduce that clinostat treatment can stimulate the raise of GAs, which induces the increment of the expression of α-amylase genes, then trig-gers the degradation of starch grains. As a result, plant can produce more active energy to respond to clinostat stimulus.