Triple-negative breast cancer (TNBC) treatment is frequently limited by both intrinsic resistance and normal tissue toxicity in radiation therapy (RT) and chemotherapy. Herein, we report reactive oxygen species (ROS)-activatable DOX prodrug loaded liposome nanoparticles (ROS-LNPs) for precision therapy against TNBC. First, the ROS-activatable DOX prodrug was prepared by chemically conjugating caspase-3-cleavable peptide (Acetyl-Lys-Gly-Asp-Glu-Val-Asp, KGDEVD) to DOX using self-immolative PABC linker, resulting in DEVD-DOX. The prodrug of DEVD-DOX is inactive and nontoxic in cancer cells, but it exhibits ROS-activatable cytotoxicity following low-dose radiation. Second, DEVD-DOX is encapsulated into 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (PS)-containing liposome nanoparticles (ROS-LNPs) to improve blood stability and uniformly penetrate into tumor tissue. The resulting ROS-LNPs form very stable nanoparticles with an average diameter of 108.1 ± 7.3 nm. In particular, ROS-LNPs exhibit low-dose radiation (5 Gy) generated ROS-activatable cytotoxicity in 4 T1 cells, wherein ROS-induced activated caspase-3 can cleave DEVD-DOX released from ROS-LNPs into free DOX that further shows the ROS-induced amplified cytotoxicity without lose-dose radiation. To overcome physiological barriers of the tumor targeting of ROS-LNPs in tumor microenvironment (TME), micro-syringe chip (MSC)-mediated intratumoral delivery strategy is employed to ensure uniform intratumoral delivery. MSC-mediated intratumoral administration of ROS-LNPs exhibit 3.26-fold higher tumor-targeting efficiency than conventional intratumoral administration in 4 T1 tumor-bearing mice. The combination of ROS-LNPs and low-dose radiation greatly suppresses tumor growth with potential anticancer immunity, such elevated ICD, dendritic cell (DC) activation, and cytotoxic T cell infiltration, in 4 T1 tumor-bearing mice. Furthermore, the combination of ROS-LNPs and low-dose radiation exhibits the minimal off-target toxicity in normal tissues. This study highlights the clinical potential of ROS-activable doxorubicin loaded liposome nanoparticles as a promising stimulus-responsive platform to bridge the gap between low-dose RT and precision chemotherapy in TNBC treatment.