Abstract:  [Objective] The efficient development of shale oil in the Yingxiongling area of the Qaidam Basin relies on horizontal well volumetric fracturing. Accurately evaluating cluster efficiency during stimulation and post-fracturing production performance remains a key challenge. This study aims to investigate the application and effectiveness of behind-casing fiber-optic sensing technology for this purpose. [Methods] Based on the principles of distributed fiber-optic sensing, this technology was deployed behind the casing to monitor fracturing operations and subsequent production in shale oil horizontal wells. The analysis focused on interpreting the monitoring data to assess fracture initiation and cluster contribution.[Results]  The behind-casing fiber-optic monitoring provided clear diagnostic results. Compared to the conventional uniform perforation method, employing a tapered perforation design increased the cluster initiation rate during fracturing from 62% to 88%, representing a 26% improvement. Furthermore, the post-fracturing production efficiency per stage was enhanced from 0.94 m³/stage to 3.20 m³/stage, a 2.4-fold increase. An additional operational finding was that controlling the fracturing operation to within 8 hours after setting the metallic dissolvable bridge plug reduced fluid loss during the treatment by 7.43%.[Conclusion]The tapered perforation strategy significantly improves both cluster initiation and production contribution in the studied shale oil formation. Furthermore, optimizing the timing of fracturing operations after bridge plug setting can effectively mitigate fluid loss. [Significance] This study demonstrates the practical value of behind-casing fiber-optic monitoring for guiding key engineering decisions. The findings provide precise guidance for optimizing perforation design and operational timing in volumetric fracturing of shale oil horizontal wells in the Qaidam Basin, contributing to enhanced stimulation effectiveness and development efficiency.