Dynamic protein complex assembly is critical for regulating various biological processes. Proximity labeling(PL), best represented by the ascorbate peroxidase APEX2, allows these molecular events to be captured in living cells in a spatiotemporal manner. However, the hydrogen peroxide (H2O2) dependence of APEX2 has hindered its application in sensitive living systems. Here, we introduce ROProx, a radical- and oxygen-driven photoreactive PL technologythat leverages the chemically evolved biotin-naphthylamine probe BN2, which has strong binding affinity for APEX2, and the unexpected tyrosyl radicals in APEX2. ROProx labels dynamic cytosolic protein complexes in living cells within seconds, with a range of 10 nm and is precisely controlled by mild blue light irradiation without H2O2. Additionally, we applied ROProx to explore the phosphotyrosine29 dependent GRB2 interactome in living mice by simply injecting BN2 for 5 minutes. ROProx should therefore open broad opportunities for PL chemical evolution and applications in other living systems.