Photothermal therapy (PTT) has received constant attention as efficient cancer therapy method due to locally selective treatment and not affected by tumor microenvironment. In this study, a novel 880 nm near-infrared (NIR) laser triggered photothermal agent (PTA), 3TT-IC-4Cl, was used for PTT of tumor in deep tissue. Folic acid (FA) conjugated amphiphilic block copolymer (folic acid-polyethylene gly-col-poly (β-benzyl-L-aspartate)10, FA-PEG-PBLA10) was employed to encapsulate 3TT-IC-4Cl by nano-precipitation to form stable nanoparticles (TNPs), TNPs exhibit excellent photothermal stability and photothermal conversion efficiency. Furthermore, the in vitro results showed TNPs display excel-lent biocompatibility and significant phototoxicity. These results suggest that 880 nm triggered TNPs has great potential as an effective PTAs for photothermal therapy of tumor in deep tissue.