After printing and sintering of the N type TOPCon (Tunnel Oxide Passivating Contacts) solar cells, the efficiency was improved significantly by light injection, which mainly manifested in the improvement of Voc and FF. The mechanism is to improve the passivation performance through adjusting the Fermi energy level by temperature and light intensity and controlling the total amount and valence state of H. The quality of the passivation film, the doping concentration of silicon substrate and the temperature during the light injection annealing process have great influence on the efficiency of the light injection annealing process. The experiments show that the lower the conversion efficiency of the battery is, the higher the efficiency is after light injection. The higher the conversion efficiency is, the smaller the defect will be, and the efficiency has almost no gain after the light injection annealing process. In addition, concentric circles can be eliminated obviously after light injection annealing process. This paper mainly studies the effects of temperature, light intensity, substrate resistivity, front surface metal contact area and poly-Si thickness on the efficiency of light injection annealing process.