Controlling　the　structural　order　of　nanoparticles　(NPs),　morphology,　and　composition　is　of　paramount　significance　in　tailoring　the　physical　properties　of　nanoassembly.　However,　the　commonly　reported　symmetrical　nanocomposites　often　suffer　an　interference　or　sacrifice　of　the　photophysical　properties　of　the　original　components.　To　address　this　challenge,　we　developed　a　novel　type　of　organic-inorganic　Janus　nanocomposite　(JNCP)　with　an　asymmetric　architecture,　offering　unique　features　such　as　the　precisely　controlled　localization　of　components,　combined　modular　optical　properties,　and　independent　stimuli.　As　a　proof　of　concept,　JNCPs　were　prepared　by　incorporating　two　photoacoustic　(PA)　imaging　agents,　namely　an　organic　semiconducting　dye　and　responsive　gold　nanoparticles　(AuNP)　assembly　in　separate　compartments　of　JNCP.　Theoretical　simulation　results　confirmed　that　the　formation　mechanism　of　JNCPs　arises　from　the　entropy　equilibrium　in　the　system.　The　AuNP　assembly　generated　a　PA　images　with　the　variation　of　pH,　while　the　semiconducting　molecule　served　as　an　internal　PA　standard　agent,　leading　to　ratiometric　PA　imaging　of　pH.　JNCP　based　probe　holds　great　potential　for　real-time　and　accurate　detection　of　diverse　biological　targets　in　living　systems.　©　2021　Wiley-VCH　GmbH