Acetone is an important industrial raw material as well as biomarker in medical diagnosis. The detection of acetone has great significance for safety and health. However, high selectivity and low concentration (ppb level) detection remain challenges for semiconductor gas sensor. Herein, we present a novel sensitive material with bimetallic PtCu nanocrystal modified on WO3·H2O hollow spheres (HS), which shows high sensitivity, excellent selectivity, fast response/recovery speed and low limit of detection (LOD) to acetone detection. Noteworthy, the response (Ra/Rg) of WO3·H2O HS sensor increased by 9.5 times after modification with 0.02％bimetallic PtCu nanocrystals. The response of PtCu/WO3·H2O HS to 50 ppm acetone is as high as 204.9 with short response/recovery times (3.4 s/7.5 s). Finally, the gas-sensitivity mechanism was discussed based on gas sensitivity test results. This research will offer a new route for high efficient acetone detection.