The deep formations of the Yingqiong Basin are situated in a high-temperature and high-pressure (HTHP) environment, characterized by a narrow formation pressure window and consequently high operational risks. Accurate prediction of Equivalent Circulating Density (ECD) is crucial for wellbore stability control and well control safety during the drilling of extended-reach wells (ERWs) in this block. Existing calculation methods fail to account for the errors in well depth and true vertical depth (TVD) measurements caused by drill string buckling, which affect the ECD calculation. Therefore, to achieve precise ECD control, this study addresses the HTHP characteristics of ERWs in the Yingqiong Basin. It takes into consideration the variations in drilling fluid performance parameters, the influence of cuttings, and the well depth/TVD measurement errors induced by drill string buckling. On this basis, the traditional ECD calculation model is modified, and a set of ECD calculation models tailored to ERWs in the Yingqiong Basin is established. This model aims to meet the requirements for fine ECD control in drilling operations within the block and reduce operational risks. By comparing the error rates between the prediction results of the traditional ECD calculation model and those of the proposed model in this study, using the on-site measured ECD data from Well LD10-X-X in the Yingqiong Basin, the results demonstrate that for HTHP ERWs in the Yingqiong Basin, incorporating the well depth and TVD measurement errors caused by drill string buckling can enhance the accuracy of ECD prediction.