Photoacoustic imaging (PAI) has emerged as an advantageous modality with high resolution and deep tissue penetration. However, its application is limited by the lack of available contrast agents. In this work, we report the synthesis of a naphthalene fused BODIPY dimer Na-BD, and the impact of the electronic structure on the oxidative cyclo-dehydrogenation process was systematically studied. Na-BD exhibited intense NIR absorption, much better photo-stability and higher PA activity compared to commercial ICG dye, which makes it an excellent contrast agent for PAI. Moreover, the in vivo PAI studies based on Na-BD loaded BSA nanoparticles were carried out and they demonstrated a significant passive targeting capacity by exploiting the enhanced permeability and retention effect in the tumor region.