Abstract: Photothermal therapy is an emerging tumor treatment method, which is mainly achieved by injecting targeted nanomaterials with high photothermal conversion rate into the tumor. In order to optimize the therapeutic effect, an effective imaging method is needed for real-time tracking the in vivo motion trajectory and accurately quantifying the intra-tumor enrichment of nanoparticles. In this study, the real-time 3D photoacoustic/ultrasound fusion imaging method is used to trace specific images of the nanoparticle enrichment process and quantitatively evaluate the enrichment patterns of the nanoparticles within the tumor body, which supports the real-time monitoring for targeted photothermal therapy nanoparticles.