The present invention relates to a method for biosynthesizing the serotonin derivatives in plants, more particularly, a method for biosynthesizing the serotonin derivatives characterized by treating plants with inducers for serotonin derivative biosynthesis or by inducing over-expression of tyramine N-(hydroxy cinnamoyl)transferase in plants. The method of the present invention facilitates the production of serotonin derivatives such as feruloylserotonin and coumaroylserotonin that have activities of anticancer, anti-oxidation and promoting bone-formation. The serotonin derivatives prepared by the method above can be used either after being purified or as edible plants themselves.