In this study, we investigated the particle network formation in poly(lactic acid) (PLA)-based nanocomposite and its influence on mechanical properties of PLA, especially on elongation at break deeply related to toughening. In order to obtain an eco-friendly PLA-based composite without sacrificing of biodegradability and biocompatibility, PLA content maintained higher than 80% of the composite. To realize toughening of PLA having inherent drawback of brittleness, natural rubber were limitedly added to PLA and hard to expect any miscibility between PLA and rubber. Meanwhile, for the stiffness-toughness balance along with high content of PLA, mineral particles are added to PLA. We expected the addition of natural rubber featuring high elongational properties and impact strength to PLA would make up its brittleness, while particles would enhance melt strength as well as biodegradability. Nevertheless of outstanding properties of each polymer, the immiscibility between PLA and natural rubber (NR) consisting of polyisoprene is a challenge to obtain synergistic effect out of melt-compounding. Depending on the distribution of the rubber phase and the interaction between rubber, PLA and particles, particle dispersed differently in PLA and the brittleness was able to be limitedly improved. Mostly the addition of natural rubber rather decreases the elongation at break of blend than improvement if the content of rubber is limited to less than 10% contents. In addition to this, the addition of mineral particles brought out different mechanical response depending on the content of particles in composite. Formation of integrated particle network rather enhanced mechanical performance as long as the morphology of rubber decreased to submicron scale which was manipulated by an interaction between phases and particles. Acknowledgment This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (No. 2016R1E1A1A01942362)