The ever increasing problem of air pollution has provoked the research and development of highly-efficient photocatalysts. Herein, Ag nanowires@TiO2 composite photocatalyst with improved photocatalytic performance was fabricated by a facile one-step solvothermal procedure. The formation of one-dimensional Ag nanowires@TiO2 core-shell nanostructures could not only broaden the light-absorbing range of TiO2 catalysts through the surface plasmon resonance effect of Ag nanowires, but also enable the effective separation of photoinduced electron-hole pairs. Under the irradiation of a 260 W fluorescent lamp, the composite with 0.5 wt % Ag nanowires exhibited the highest photocatalytic activity in short contact time (4.8 min), and the corresponding gaseous acetaldehyde removal ratio was 72%, which was much higher than that of bare TiO2 (37%). The photocatalyst also showed ultrastable activity in the 15 weeks usage, which ensured their practical applications in the air purification field. An in-depth mechanism of the photodecomposition of acetaldehyde was proposed on the basis of the electron spin resonance (ESR) tests and the scavenger experiments. O-center dot(2)- reactive radicals was found to play a predominant role in the oxidation and decomposition of acetaldehyde. The outstanding performance of the composite materials and the thoroughly understanding of the reaction mechanism would cast light on the purposively design and optimization of TiO2-based catalysts.