Oxygen isotope of phosphate (δ¹⁸O_P) was a very effective proxy for tracing sources. Due to the complicated composition of lake sediments, samples must be treated by carbon elimination and purified before the δ¹⁸O_P measurement. In order to establish a suitable pretreatment method for δ¹⁸O_P of lake sediments, this study compared several widely-used pretreatment methods, including organic carbon elimination by NaClO treatment and H₂O₂ treatment, purification by Blake method and McLaughlin method. The results showed:(1) NaClO kept high inorganic phosphate extract ratios, and removed organic matter efficiently with less impacts on different phosphate species. The organic removal efficiency by H₂O₂ was not stable while the phosphate species changed after treatments and inorganic phosphate concentration increased significantly. (2)Ammonium phosphomolybdate(APM)+ ammonium phosphate(MAP)and CePO₄ was used by Blake method and McLaughlin method,respectively. Blake method had better performance on the purification of lake sediments samples than McLaughlin method, and a higher organic matter removal rate than McLaughlin method with stable phosphate throughput. (3) The Ag₃PO₄ produced by the Blake method had lower C, N contents and better repeatability than the McLaughlin method. The advantages of both the NaClO treatment and the Blake method were made full use to establish an improved δ¹⁸O_P pretreatment method for lake sediments with modified procedures. It is recommended to use 2.5% NaClO to remove organic matter before phosphate extraction, and then purify the phosphate extractions through MAGIC, APM+MAP, and cation resin treatment, in turn.