The performance improvement of Rubrene/C₇₀ based organic solar cells ( OSCs) with WO_3as buffer layer is studied in this paper.The OSCs with the structure of ITO/WO  3/Rubrene/C₇₀/BCP/Al were fabricated．WO_3was used as anode buffer la yer,inserted between ITO and Rubrene.The performance and mechanism of the OSCs are studied by inserting WO_3with different thicknesses as buffer layer．The experimental results show that the characterist ic parameters of the OSCs, including the short-circuit current(J_sc),open -circuit voltage(V_oc),filling factor (FF), series resistance (Rs) and power convers ion efficiency (PCE),have a regular change with different WO_3thicknesses as buffer layers.The PCE of the OSCs i s increased with the increasing thickness of WO₃,when the thickness is smaller than 80nm.The PCE of the OSCs is decreased with the increasing thickness of WO₃,when the thickness is larger than 80nm.T he PCE of the device is as high as 1.03% with 80nm-thick WO_3while the J sc ,V_oc,FF and R_s of the O SCs are 2.81mA·cm－2,0.83V,43.85% and 45.3Ω·cm²,respectively.Compared with the device without buffer layer,t he J_sc,Voc,FF and PCE of the OSCs are enhanced by 31%,137%,17% and 268%,respectively．Rs is reduced by 33%.