Photothermal therapy（PTT）is a kind of tumor treatment that irradiates photothermal agent（PTA）by external light source to convert light energy into heat energy to kill tumor cells. It has the advantages of strong targeting，little invasion and few adverse reactions. Photothermal agent（PTA）is one of the key factors that determine the effect of photothermal therapy. Croconaines（CR）and their nanoparticles have been used as PTA and achieved good PTT effect in tumor in recent years，due to their strong near-infrared （NIR）absorption，high photothermal conversion efficiency and excellent chemical and thermal stability. In this paper，the molecular structures of croconaines used for photothermal therapy reported in the literatures and the effect of structural modification on photothermal properties were summarized，and the tumor photothermal therapy effect of croconaine nanoparticles was described，which provided new ideas for the development of efficient photothermal diagnosis and treatment reagents.