The present invention relates to a use of phthalides in the preparation of medicinal composition for facilitating the oxygen release of hemoglobin-based blood substitutes, wherein the hemoglobin can be fetal hemoglobin or other hemoglobin variants that retain two α subunits. The phthalides can play a functional role similar to 2,3-BPG in modulating the allostery of Hb-based blood substitutes to lower the oxygen affinity, and can therefore act as the 2,3-BPG substitute to bring the oxygen release function of Hb-based blood substitutes to the same level as that of normal hemoglobin, and therefore to sustain the normal cellular oxygenation level.本發明係關於一種苯酞類化合物用於製備提升血紅蛋白類血液代用品之氧氣輸送功能之醫藥組合物的用途,其中該苯酞類化合物具有提升血紅蛋白類血液代用品之釋氧率之功效,其中該血紅蛋白類血液代用品為胚胎血紅蛋白(HbF)或其他保有二個α次單元之變異血紅蛋白。該苯酞類化合物用於替代/協助2,3-二磷酸甘油酸,扮演2,3-二磷酸甘油酸代用物之角色,協助血紅蛋白類血液代用品得以更有效取代正常血紅蛋白之釋放氧氣至組織細胞之生物功能,使細胞含氧量維持在正常範圍。