Abstract: The Ying-Qiong Basin in the western sea area of South China Sea is characterized by high geothermal gradient and high pressure coefficient, so high-density drilling fluid is needed in HTHP hole sections. However, the application of high-density drilling fluid results in narrow safety density window, and coexistence of leakage and blowout in the process of well drilling. In order to increase drilling safety and efficiency of HTHP wells, reaming while drilling (RWD) technology is used to improve casing program so as to provide the favorable safety window for drilling operation. In this paper, one HTHP well in the Ying-Qiong Basin was taken as an example. Its drilling difficulties and the corresponding countermeasures were investigated. Then, the RWD process was analyzed from the aspects of technical suitability, reaming tool selection, size selection of reaming tools and pilot bits, vibration analysis and hydraulic analysis of reaming tool, and key factors of field technologies. And thus, the RWD technology is developed.