The fully biodegradable polymer blends remain challenges for the application due to their undesirable comprehensive performance. Herein, remarkable combination of superior mechanical performance, bacterial resistance, and controllable degradability is realized in the biodegradable poly(L-lactide)/poly(butylene succinate) (PLLA/PBSU) blends by stabilizing the epoxide group modified titanium dioxide nanoparticles (m-TiO2) at the PLLA-PBSU interface through reactive blending. The m-TiO2 can not only act as interfacial compatibilizer but also play the role of photodegradation catalyst: on the one hand, binary grafted nanoparticles were in situ formed and stabilized at the interface to enhance the compatibility between polymer phases. As a consequence, the mechanical properties of the blend, such as the elongation at break, notched impact strength and tensile yield strength, were simultaneously improved. On the other hand, antibacterial and photocatalytic degradation performance of the composite films was synergistically improved. It was found that the m-TiO2 incorporated PLLA/PBSU films exhibit more effective antibacterial activity than the neat PLLA/PBSU films. Moreover, the analysis of photodegradable properties revealed that that m-TiO2 nanoparticles could act as a photocatalyst to accelerate the photodegradation rate of polymers. This study paves a new strategy to fabricate advanced PLLA/PBSU blend materials with excellent mechanical performance, antibacterial and photocatalytic degradation performance, which enables the potential utilization of fully degradable polymers. [ABSTRACT FROM AUTHOR]