Targeted drug delivery and controllable generation of oxygen-independent toxic free radicals in tumor hypoxia environments are of great importance in cancer therapy. Here, a thermoresponsive nanoplatform was introduced by modifying carbon-coated iron carbide (FeC) nanoparticles with bovine serum albumin (BSA) to achieve better water solubility and biocompatibility. Then a type of polymerization initiator (AIPH) was effectively loaded on the surface of FeC-BSA nanoparticles and sealed by a phase change material (PCM) for higher drug loading and controlled drug release stimulated by heat. Upon illumination by near-infrared light, the photothermal effect of FeC nanoparticles melts the PCM, triggering the release of encapsulated AIPH to produce free radicals, which effectively kill the hypoxia cancer cells. Additionally, the special magnetic performance enables targeted and tracked therapy under the driving of an external magnetic field. What's more, the as-prepared multifunctional theranostic nanoplatform (FeC-BSA-AIPH/PCM) ingeniously combine magnetic targeting, remotely controlled drug delivery, the generation of free radicals independent of oxygen levels into a single nanoparticle for effective cancer treatment, in detail, causing cancer cells death in vitro and markedly inhibiting tumor growth in vivo. This work presents a paradigm demonstrating that enhancing the therapeutic effect based on rationally designed multifunctional nanotheranostic agent will pioneer a new way for synergistic cancer treatment and highly developing nanotechnology.