Abstract: In the multi-unit level 1 probabilistic safety assessment (PSA) study, the modeling workload greatly increases due to the increase of the number of units, which brings difficulties to the risk assessment of the whole nuclear power plants. Based on the existing foundation, the method for preliminary evaluation of initiating event consequences in a site was studied in this paper. The calculation method of core damage frequency (CDF) upper and lower bounds was used to analyze the influence of the number of units on CDF in the site. The results show that the two-unit site is suitable for priority analysis. In view of the dual-unit site, the initial events within the multi-unit site were screened. The results show that the loss-of-offsite-power (LOOP), loss of heat trap and other events are suitable for modeling and analysis. Recommendations were also made for other screening results. This paper provides an important basis for the modeling of the level 1 PSA subsequent accident sequence at multi-unit sites.