<b>Optimization of Rod String Design for the Sucker Rod Pumping System in Mann Oil Field</b> This research aimed to present properly rod string design and to prevent rod failures in sucker rod pumping wells. The great majority of the world`s oil wells need some kinds of artificial lift methods to produce the oil to the surface. Sucker rod string should be properly designed to provide failure free pumping operation for an extended period of time. Rod string design usually aims at the determination of 1 the rod sizes to be used in the string, 2 the length of individual taper sections and 3 the rod material to be used and 4 the maximum allowable stress for rod string. If improper design of sucker rod string is employed and the working or actual stress is greater than the permissible stress, the rod string will be in premature rod failure. Detail calculations are performed with a proper consideration of actual well conditions by using geological configuration and the historical production data from Mann oil Field in Myanmar. In this research paper, some theories of the West’s method, Neely’s method and Equal Service Factor method are used to design by using of the well data to install the proper design and improve the production rate. sucker string design, rod side, stress, failure and production rate 2306-2311 Issue-5 Volume-3 San Win