Trans-cinnamaldehyde, the main component of volatile oil from cassia twig or Cinnamomum cassia, which is a traditional Chinese herbal medicine. Trans-cinnamaldehyde is a kind olefine aldehyde of organic compounds and has many pharmacological properties, such as anti-inflammatory, anti-tumor, anti-bacterial, antidiabetic, anti-obesity, and neuroprotection etc. The compound has preventive and therapeutic effects on the nervous system, cardiovascular, cancer, diabetes and other diseases. Trans-cinnamaldehyde, as a preventive care of nature medicine, has great clinical and market potential. This paper gives a review about the pharmacological effects and mechanism of trans-cinnamaldehyde researched in the latest five years. We hope to provide some basic information for further research on trans-cinnamaldehyde.