Photodynamic antimicrobial chemotherapy (PACT) is a promising therapy against biofilm infection. However, due to the saliva clearance and obstacle of biofilm, the photosensitizer is difficult to concentrate in the infection site; then, the PACT is less effective on oral biofilm infection. In this article, we report a special nano-antibacterial agent (SiO[sub.2]-P[sub.Ce6-IL]) to solve the bottleneck problem of PACT in treatment of oral biofilm infections. The SiO[sub.2]-P[sub.Ce6-IL] was composed of SiO[sub.2] and poly ionic liquid photosensitizer (P[sub.Ce6-IL]) and had tri-fold features of eliminate biofilm infection: high binding ability, breaking biofilm barriers, and enrichment photosensitizer in infection site. In oral biofilm, the SiO[sub.2]-P[sub.Ce6-IL] changed to SiO[sub.2]-P[sub.IL][sup.+] like claws of octopus that could hold tightly with biofilm. Then, the poly-dodecyl on the SiO[sub.2]-P[sub.IL][sup.+] broke down the barrier of biofilm. The results of HR-MS and zeta potential indicated that SiO[sub.2]-P[sub.Ce6-IL] could change to positive (SiO[sub.2]-P[sub.IL][sup.+]) in acidic environment. The interaction forces and morphology results proved that the SiO[sub.2]-P[sub.IL][sup.+] had a higher affinity to biofilm and could destroy the biofilm structure. Then, the photosensitizer was enriched in biofilm at sites of infection. The in vitro and in vivo experiments showed that SiO[sub.2]-P[sub.Ce6-IL] could effectively eradicate oral biofilm infections and control of dental caries.