The nanostructured p-n heterojunction has been synthesized by solution method. The n-type ZnO nanowires were hydrothermally synthesized on a glass substrate; meanwhile, the p-type CuMnO2 was deposited on n-type ZnO nanowires by the sol-gel method. It is well known that solution synthesis has the advantages of large area, low cost, and high efficiency. The n-ZnO/p-CuMnO2 core-shell nanowires revealed rectification and ultralow-leakage properties. The crystalline structures of the p-CuMnO2 and n-ZnO nanowires were amorphous and single crystal, respectively. The organic gas-sensing ability of the CuMnO2/ZnO NWs is very sensitive and fast (~4 s); in addition, the photo-response to UV (365 nm), blue (445 nm), and green (520 nm) illumination was 6.3 × 105, 4.3 × 103 and 50.5, respectively. The above results prove that p-n heterojunction can improve the gas sensing and photo-response of nanomaterials.