The stacked passivation films for emitter of TOPCon solar cells were investigated in the paper. The passivation performance of three different stacked films (SiO2/SiNx, Al2O3(1.5 nm)/SiNx, SiO2/Al2O3(1.5 nm)/SiNx) were compared. The results show that the Al2O3 (1.5 nm)/SiNx films exhibit better passivation performance than that of the SiO2/SiNx films, and the SiO2/Al2O3(1.5 nm)/SiNx films perform the best, with an implied open circuit voltage of 705 mV. Based on the Al2O3/SiNx stacked passivation films, the effect of Al2O3 thickness (1.5 nm, 3 nm and 5 nm) on the passivation performance and photoelectric conversion efficiency of cells were investigated. When the thickness of Al2O3 increases from 1.5 nm to 3 nm, the passivation performance is significantly improved, the mean value of the implied open circuit voltage increases by 20 mV to 707 mV, and the conversion efficiency of the corresponding cells increases by 0.23 percentage point, which is comparable to that of the SiO2/Al2O3(1.5 nm)/SiNx stacked films cells. However, when the thickness of Al2O3 continues to increase to 5 nm, the mean value of the implied open circuit voltage remains unchanged. Therefore, Al2O3(3 nm)/SiNx stacked films can be used to replace the SiO2/Al2O3(1.5 nm)/SiNx stacked films, which not only simplifies the process flow of the solar cells, but also reduces the production cost.