Background: This study investigated the effect of PARPi as maintenance therapy after 1st-line and 2nd-line chemotherapy on platinum sensitivity in patients with recurrent high-grade serous epithelial ovarian cancer (rHGSOC). Methods: 172 patients with rHGSOC at Zhejiang Cancer Hospital and Jiaxing Maternity and Child Health Care Hospital from Jan 2017 to Dec 2021were retrospectively analyzed. Patients who received PARPi as maintenance therapy after first-line chemotherapy were enrolled to the 1st-PARPi group (n=23), and subjects who did not receive PARPi maintenance therapy were enrolled to the 1st control group (n=105). Similarly, 2nd- PARPi group (had not use PARPi in first-line treatment n=30), 2nd-control group (n=89) were divided. To evaluate progression-free survival (PFS), the first progression to second progression (TTSP), the second progression to third progressio (TTTP), PFS between the second progression and the end of the second-line chemotherapy (PFSs), PFS between the third progression and the end of the third-line chemotherapy (PFSt) and to compare whether PARPi as maintenance therapy affects the platinum sensitivity of these patients. Results: PFSs in 1st-PARPi vs.1st-control group (median 5 vs. 11 m; p=0.0037). PFSt in 2nd-PARPi vs. 2nd-control group(median 4.5 vs. 9.0 m; p=0.0009). TTSP in 1st-PARPi vs. 1st-control group (median 11 vs. 16 m; p=0.0045). TTTP in 2nd-PARPi vs. 2nd-control group (median 10 vs. 15 m; p=0.0007). Among the 23 patients in 1st-PARPi group and 105 patients in 1st-control group, 9 and 99 patients were platinum sensitive while 14 and 6 patients were platinum resistant respectively (HR 14.46, 95% CI =4.07-51.53, P < 0.0001). Among the 30 patients in 2nd-PARPi group and 89 patients in 2nd-control group, 10 and 71 patients were platinum sensitive while and 20 and 18 patients were platinum resistant respectively (HR 4.37 95% CI=1.98-9.64, P < 0.0001). Age, stage, residual tumor after initial surgery treatment and the courses of platinum-based chemotherapy before PARPi,BRCA gene mutation were not the related factors affecting the platinum sensitivity of next line chemotherapy. There was no statistical difference in the effect of duration of PARPi on the platinum sensitivity of next line chemotherapy (duration of PARPi≥ 18 months vs. <18 months in 1st-PARPi group, HR 0.60, 95% CI=0.18-2.04, P=0.41; duration of PARPi≥ 12 months vs. <12 months in 2nd-PARPi group, HR 0.62, 95% CI=0.26-1.48, P=0.24, respectively). Conclusions: Patients with rHGSOC using PARPi affected the platinum sensitivity and were more likely to lead to platinum resistance no matter how long the during of PARPi were.This conclusion was consistent with the cross resistance between PARPi and platinum. Care should be taken when using PARPi after 1st-line and 2nd-line chemotherapy as maintenance therapy.