Background: PARP inhibitors (PARPi) have shown significant clinical benefit as maintenance or systematic therapy in patients with ovarian cancer (OC) with BRCA1/2 mutation or positive homologous-recombination deficiency (HRD) status. However, patients with BRCA1/2 mutation not only showed better efficiency of PARPi, but also higher HRD score than other populations. Therefore, patients with BRCA1/2 mutation have received much attention. However, there are many kinds of variants in BRCA1/2 of OC patients. The purpose of this study is to explore the distribution of BRCA1/2 copy number variation (CNV) in OC patients and its association with HRD score. Methods: A crosssectional analysis of 1636 OC patient who were retrospectively analyzed with a customized 3D-HRD panel (panel of Next-generation sequencing) between 2020 and 2022 was carried out. The HRD score was calculated as the sum of the LOH, TAI, and LST and we defined HRD score more than 30 and deleterious BRCA1/2 mutation as HRD positivity.