As one of the crucially important oxide 1D nanostructures, tungsten oxide (WO₃) nanowire holds great promise for diverse applications range from the electrochromic to high performance of catalysis, sensors, photoelectric catalyst for water splitting, etc. However, although great efforts have been made to elongate the WO₃ nanowire, the length of the as-grown nanowire is still limited at several tens of micrometers, which impedes its extensively applications in the flexible and wearable electronics. Here, we firstly realize the millimeter-level WO₃ nanowire growth and demonstrate the feasibility of such ultra-long WO₃ nanowire integrated with the flexible substrate for the molecule sensing application. It is found that the ultra-long WO₃ nanowire constructed flexible sensor presents a superior sensing performance and mechanical robustness to the lung cancer biomarker molecules. The detail synthesis method, nanowire growth mechanism and performance of the flexible WO₃ nanowire sensor will be presented at the meeting.