Photo-thermal therapy (PTT) is based on localized heating by light absorption for selective ablation of abnormal cells. PTT is highly selective to diseased sites, minimally invasive to normal tissues, and antiseptic in comparison with traditional therapies. The key component of PTT is photothermal transducers that can absorb and convert near-infrared light (NIR) into heat with high efficiency. Up to date, a variety of NIR photothermal transducers have been developed. Application of NIR photothermal conversion nano-materials in imaging-assisted PTT as well as its development trend is focused in this review.