The extraction process for Sr-Y separation with HDEHP was studied, including the medium of aqueous phase and its acidity for separation, the washing conditions for the extractant after extraction, and the medium of aqueous phase and its acidity for stripping. After these studies, a suitable separation process was obtained. By using the process, yttrium can be separated from Sr-Y mixed solution The recovery of Y was more than 90% after a separation process, and the impurity of Sr in Y solution was less than 2 × 10-6. HDEHP can be used as the separation material for the medical 90Y preparation