Mercury ion(Hg²⁺) is one of the most toxic heavy metals that has severe adverse effects on the environment and humans. Therefore, more and more attention has been paid to developing analytical approaches for the rapid detection of Hg²⁺. Nanomaterials are widely used for Hg²⁺ detection due to their potential optical advantages and stability. The nanosensors for Hg²⁺in recent years are highlighted in this review. According to the composition of nanomaterials, these sensors can be divided into nanosensors based on gold, silver, carbon and silicon nanomaterials, quantum dots, organic nanoparticles and other nanomaterials. These nanosensors are described and discussed respectively in terms of design principle, identification performance and practical application. Finally, the research prospect in this field is presented.