The invention discloses an OLED structure optimization design method and device and belongs to OLED field. The method includes the following steps: step 1, determining the working wavelength lambda ofOLED, the optical constant of each layer material of OLED, the initial design thickness value of each layer material of OLED and the azimuth of the main axis of anisotropic material in OLED, theta and psi; step 2, establishing the multi-layer stack optical model of OLED based on the parameters identified in step 1 and adjusting the thickness of cathode, cathode finish layer, luminous layer, holetransport layer, hole injection layer, anode and the layer to be optimized in the substrate. The simulation test is conducted to obtain the external coupling efficiency of OLED at different structurethicknesses and determine the maximum structural thickness of external coupling efficiency. The device is used to executive the above method. The method has the advantages of simple principle and easy-to-operate and can realize the simulation optimization calculation of OLED structure dimension.