Over the past years, polymer solar cells have been widely investigated as the potential renewable energy source because of their low-cost, light-weight, flexible and large area fabrication technology via ink-jet printing. The current performances of state-of-the art polymer solar cells have increased to more than 10% through various materials development and device engineering. One of the challenges to further improve the performance is the new low band-gap polymer development, in those reported low band-gap polymers, only a few of them could provide a high and repeatable photovoltaic performance with device optimization. Understanding the relationship between structure and performance is curial to develop and design high performance polymers. Herein, we reported a significant side chain effect on the photovoltaic performance in the novel beznodithiophene and quinoxaline-based polymers. By changing the side chain position, we found the two polymers have total different optical, cyclic voltammetry properties. The photovoltaic performance varied from 0.69% to 4.54%. In this conference, we will give the detail report in these optical, cyclic voltammetry, FET, and photovoltaic properties.