Abstract: This paper selects three different sizes of 182 half piece bifacial glass PERC mono-Si PV modules（numbered A、B、C）,under indoor testing conditions,firstly,test the response characteristics of PV modules A and B to different incident angles to analyze the impact of incident angles on the performance of PV modules of different sizes. Then test the electrical performance and reflectivity of PV module C in its initial state and with slight dust on its surface,as well as its characteristics at different incidence angles,to analyze the impact of slight dust on the performance of large-sized bifacial glass PV modules. The research results indicate that:1) When the incident angle is between-85 ° and 85°,the reduction in short-circuit current of the two largesized bifacial glass PV modules is basically the same as the increase of the incident angle. This means that the reduction in short-circuit current at different incident angles is not affected by the size of the PV module. 2) When the incident angle is less than 60°,the relative transmittance of both large-sized bifacial glass PV modules is close to 1,and the relative transmittance of the relatively large-sized PV modules is slightly higher overall.3) When the incident angle exceeds 70°,the relative transmittance of the PV module decreases sharply,leading to a sharp increase in output current loss. Therefore,in the actual use of PV modules,it is necessary to avoid situations where the incident angle exceeds 70°. 4) Under three different reflectivity conditions with accumulated dust,there is little change in the open circuit voltage of PV modules,indicating that different dust accumulation states have a relatively small impact on the open circuit voltage of PV modules,but their impact on the shortcircuit current is very significant. As the reflectivity increases,the short-circuit current of PV module C gradually decreases,and the maximum power also gradually decreases. But when there is not much dust accumulation and the reflectivity is not high enough,a balance should be sought between the cost of cleaning the accumulated dust and the efficiency of power generation.