Rosmarinic acid, a polyphenol-containing hydroxy acid, is believed to have many activities, such as anti-oxidation, anti-inflammatory, immune regulation, anti-thrombosis generation, anti-baterial, anti-virus and anti-depressants. It is used commercially for food preservation. Here we report that rosmarinic acid extended the lifespan of the model organism Caenorhabditis elegans (C. elegans) under normal culture conditions (25°C) and under thermal stress (35°C). C. elegans dieted rosmarinic acid with final concentration 50mg / L and 100mg / L under two kind of conditions were shown to have extended lifespan compared to the control without rosmarinic acid uptake. Furthermore, the rosmarinic acid with final concentration 50mg/L had more obvious longevity-extending effect. The precise mechanism (s) responsible for this remains to be identified. To study the anti-senescence molecular mechanism of rosmarinic acid, semi-quantitative RT-PCR was used to analyze the expression of aging-associated genes such as daf-16 and heat shock protein 16.2 (hsp-16.2). As a result, the expression of aging-associated genes was up-regulated. This study suggested that rosmarinic acid significantly extends the lifespan of C. elegans through up-regulating some genes' expression such as daf-16 and hsp-16.2 which will provide important reference for antiaging research of rosmarinic acid.