The oxygen isotope ratio in phosphate (delta 18OP) is an effective tool for tracing the sources of phosphorus (P) and their biogeochemical cycles. The HCl-extractable inorganic phosphate (HCl-PTI) is the primary component of P and plays a key role in the dynamic transformation of P in sediment and soil. However, it has always been difficult to purity sample for analyzing the delta 18OP composition of HCl-PTI due to the significantly interference of large amounts of Fe2+/3+, Ca2+, Cl- and other impurities in the HCl-PTI extracts. In this study, we developed a simple and promising purification method for delta 18OP analysis of HCl-PTI in sediments and soils based on the superior selective enrichment and elution abilities of phosphate (PO4) and efficient synchronous removal of impurities by Zr-Oxide gel in highly acidic HCl-PTI extract. The enrichment rate and elution rate of PO4 in the HCl-PTI extract by the Zr-Oxide gel could achieve 100% respectively, and the synchronous removal rates of most anions, dissolved organic carbon (DOC), metals, and trace elements could be above 96% respectively, reducing the tedious operation of conventional methods and the difficulties in removal of impurities, such as Cl- in HClPTI extract. It's indicated that the purity of the Ag3PO4 solid for delta 18OP composition analysis of HCl-PTI could reach 99.9%. The above results show that the new method is very simple, efficient and reliable for the delta 18OP analysis of HCl-PTI in sediments and soils. This study provides new methodological support for identifying the sources of P and tracing their biogeochemical cycles in sediment or soil environment.