In this study, a time-resolved laser photometer was applied to measure the real-time variations in transmission, reflection, and scattering during the nanosecond laser irradiation of bulk fused silica. The time-resolved process of multi-pulse accumulative damage can be obtained via the multiple dynamic measurements in a single region till the damage occurs. The results show that the transmission considerably decreases during the pulse irradiation process prior to the occurrence of damage, and the backward reflectivity simultaneously increases, even up to 70%. The increase in the backward reflectivity is almost equal to the decrease in the transmission. The statistical analysis results show that as long as there exists backward reflection during multi-pulse irradiation, damage can occur. Stimulated Brillouin scattering promotes the multi-pulse-induced damage in bulk fused silica.