Disclosed is a novel means for preparing a platelet solution replaced with an artificial preservation solution, said platelet solution having excellent performances of inhibiting platelet activation, recovering platelets and removing plasma. A method of the present invention for preparing a platelet solution replaced with an artificial preservation solution comprises: a filtration step for, under the conditions represented by formula (1), using a separation membrane, said separation membrane having an average pore size of 0.1&mgrm or more but less than 2.0 &mgrm in the surface to be in contact with a platelet solution, cross-flow filtering the platelet solution at an inlet wall shear rate of 25-1500 s-1 to give a concentrated platelet solution and a mixing step for mixing the concentrated platelet solution with an artificial preservation solution to give the platelet solution replaced with the artificial preservation solution. Formula (1): 1.01011<(AB)/(&GgrmgrP)<=2.51013(platelets/(hrm2Pa) A: concentration of platelets contained in platelet solution (platelets/mL in the range of 8.0107-200107 platelets/mL) B: filtration flow rate per area (mL/hr/m2) &Ggr: inlet wall shear rate (s-1) &mgrP: viscosity (Pas) of platelet solution.本發明揭示用以製造具有血小板之活性化抑制性能、高血小板回收性能及高血漿去除性能之置換人工保存液之血小板溶液之新穎手段。本發明之置換人工保存液之血小板溶液之製造方法係具備過濾步驟及混合步驟;該過濾步驟係於下述式1所表示的條件下,使用與血小板溶液接觸的面之平均孔徑為0.1μm以上且小於2.0μm之分離膜,以25~1500s-1之入口管壁剪切率(wall shear rate)將前述血小板溶液交叉流過濾(cross flow filtration)而獲得濃縮血小板溶液;該混合步驟係將前述濃縮血小板溶液與人工保存液混合而獲得置換人工保存液之血小板溶液;1.0×1011<(A×B)/(γ×μP)≦2.5×1013(個/(hr‧m2‧Pa))‧‧‧‧式1A:血小板溶液所含的血小板濃度(個/mL;惟,8.0×107~200×107個/mL)B:每單位面積之過濾流量(mL/hr/m2)γ:入口管壁剪切率(s-1)μP:血小板溶液之黏度(Pa‧s)。
