Ovarian cancer is a malignant tumor that seriously threatens the safety of women's life. Chemotherapy is an important treatment for ovarian cancer. Although the initial response rate of ovarian cancer patients to chemotherapy is high, most patients will still relapse and die. After a first-line chemotherapy of paclitaxel and platinum drugs, a study has shown that after chemotherapy, the initial response rate in advanced patients is as high as 80%, but 70% to 80% of patients eventually relapse. Although the chemotherapy regimen of ovarian cancer has been improved, the efficacy of ovarian cancer has not been fundamentally improved, The 5-year survival rate is still at 30% to 45%. The ubiquitous phenomenon of chemotherapeutic drug resistance is the central link that leads to the failure of chemotherapy and the improvement of survival rate. How to solve the problem of chemotherapeutic drug resistance in ovarian cancer is one of the difficulties in the treatment of ovarian cancer at present. The high frequency of tumor cell resistance suggests the occurrence of specific molecular mechanisms within the tumor, Using second-generation sequencing technology to detect tumor-specific molecular changes in the blood circulation. The real-time and dynamic detection of the whole genome information of tumor has broad application prospects in exploring the molecular mechanism of tumor drug resistance recurrence and transforming ctDNA from basic research to clinical application.