Disclosed are a Piper laetispicum extract and a preparation method therefor and a use thereof. The Piper laetispicum extract comprises any one of sesamin, (2E, 6E)-N-isobutyl-7-(3, 4-methylenedioxyphenyl)heptadienamide, (2E, 4E)-N-isobutyl dodeca-2, 4-dienamide, (2E, 4E)-N-isobutyl-15-phenyl-2, 4-dienamide, (2E, 4E, 14Z)-N-isobutyleicosane-2, 4, 14-trienamide, (2E, 4E)-N-isobutyl-13-phenyl-2, 4-dienamide or a combination of the above. The Piper laetispicum extract can prevent depression.