In photovoltaic power generation technology, amorphous silicon thin film solar cells are widely used because of its high light transmittance, low light power generation, low price and other advantages. The research on improving the efficiency of amorphous Si thin film solar cells by optimizing the back electrode area has not been reported in industrial production. In this paper, the 5020-9 battery of Pengan Jinshi Solar Cell Technology Co., Ltd. is taken as the research object, and the influence of back electrode design on the performance of amorphous silicon solar cell under PECVD coating process and back electrode screen printing mode is discussed. The results show that under the condition that the boundary dimension is 50 mm×20 mm and 9-junction (PIN junction) must be connected in series, the optimized back electrode battery shows better photoelectric conversion performance. The average values of short-circuit current, open circuit voltage, maximum power and filling factor are 7.13 mA, 7.04 V, 12.41 mW and 25.36%, respectively. Compared with the original design, the short-circuit current increases about 47%,and the yield increases about 58%. The basic principles of the back electrode design of integrated battery are as follows: to ensure the area of each single back electrode is equal as far as possible, so as to improve the overall current matching degree; to optimize the relative position of laser etching line and increase the area of active area.