Top-down nanostructure engineering and band engineering are promising methods for fabricating efficient photocatalysts with enhanced optical and electronic properties; however, composites with simultaneously engineered structure and band are very rare. Herein, we constructed a unique architecture composed of a W18O49 nanowire alignment core and porous BiOCl shell (WA@BiOCl), which combined the advantages of both an assembly structure and a type II core-shell heterojunction. The W18O49 alignments (WA) were synthesized using a "one-pot" solvothermal treatment of WCl6/NaNO3via NO3(-)-mediated assembly, whereas the W18O49 nanowires with BiOCl shell (W@BiOCl) were obtained using WCl6/BiCl3. Then, WA@BiOCl, in contrast to W@BiOCl alignments, were fabricated when WCl6 and Bi(NO3)3 were present in the starting mixture. Optical absorption, photoelectrochemical measurements and photoluminescence characterizations show that either the alignments or the core-shell heterojunctions can enhance light harvesting, photo-charge transfer and collection. As a synergetic result, the WA@BiOCl architecture exhibited very high photoactivity and photostability. Under UV-vis (or vis) irradiation, WA@BiOCl is 2.43 (1.93), 3.93 (2.73) and 5.34 (3.44)-fold more active than W@BiOCl, WA and W18O49, respectively. The results demonstrate that the simultaneous nanostructure and band engineering can produce a more efficient photocatalyst than a single strategy alone, which suggests a potential method for the fabrication of photocatalysts in the fields of environment and energy.