1. A method of eliminating organic light emitting display (OLED) display panel Mura, comprising steps of: step 1, providing an OLED display panel and a brightness capturing device, and the OLED display panel is made to show a gray scale to be compensated; step 2, employing the brightness capturing device to capture actual brightnesses of respective sub pixels of the OLED display panel at a present display gray scale; step 3, capturing preset target brightnesses of the respective sub pixels, and a gamma value of the OLED display panel, and obtaining a compensation gray scale utilized for achieving the preset target brightnesses of the sub pixels with calculation of the following calculation formula: Gray i + 1 = ( L goal L i ) 1 γ × Gray i , wherein i is an integer larger than or equal to 0, and i+1 is a number of a present iterative computation, and L goal is the target brightness of the sub pixel, and L i is the actual brightness of the sub pixel at the present display gray scale, and γ is the gamma value of the OLED display panel, and the Gray i is the present display gray scale, and the Gray i+1 is the compensation gray scale; step 4, making the OLED display panel to show a compensation gray scale obtained by a present calculation to determine whether a preset condition of ending the calculation of the compensation gray scale is achieved; if the condition of ending the calculation of the compensation gray scale is not achieved, then returning back to the step 2; if the condition of ending the calculation of the compensation gray scale is achieved, then ending the method.