Mental disorders related to the imbalance of neurotransmitters, which are substantially affected by gut microbiota. Gut microbiota impacts on mental health by regulating the level of neurotransmitters in the host. To understand the influence of gut microbiota on mental health via neurotransmitters, we conducted a literature survey on the association between gut microbiota and neurotransmitters. We identified trustworthy evidences by critically appraising the related articles in terms of its evidence level. This paper provides a fairly comprehensive list of gut microbiota strains that can regulate neurotransmitters. Gut microbiota, neurotransmitters and mental disorders influence each other in a bidirectional way which form a triangle relationship. Understanding the triangle relationship benefits for the treatment of mental disorders. People who have experienced mental disorders may cure in the future by altering gut microbiota.