Abstract: The trans-esterification system for trans-esterifying a triglyceride includes a reaction tank, a separation tank, a first pipe and a second pipe. The reaction tank is inputted with the triglyceride and a monohydric alcohol for undergoing a trans-esterification reaction to produce a mixture. The separation tank is inputted with the mixture for a phase separation to generate an ester phase solution and a glycerol phase solution having a first part and a second part. The first pipe connects the reaction tank and the separation tank, and transports the mixture from the reaction tank to the separation tank. The second pipe connects the reaction tank and the separation tank, and transports the first part of the glycerol phase solution from the separation tank to the reaction tank for undergoing the trans-esterification reaction.