Electroluminescence (EL) defects and different process influencing factors of mono-crystalline silicon solar cells are analyzed by experimental comparison method. The open circuit voltage, short circuit current, fill factor and photoelectric conversion efficiency of the solar cells were tested, and the EL defect proportion of the solar cells is collected. It is found that the paste, sintering process, and the silicon wafer are the main causes of the EL defects. The quality of paste, the parameters of screen-printing, the stability of sintering process and the anti-reflection and passivation effect of coating process have some effects on the photoelectric conversion efficiency of solar cells. It is suggested that improving the sintering process stability, using better performance of paste and silicon wafer and optimizing the parameters of screen-printing and the flow ratios of ammonia and silane can improve the EL defect and promote the photoelectric conversion efficiency and qualified rate of solar cells.