Background: To quantify flow changes in choriocapillaris (CC) in patients with chronic central serous chorioretinopathy (CCSC) in the treatment of half-dose photodynamic therapy (PDT) using optical coherence tomography angiography (OCTA).Methods: A total of 28 affected eyes and 24 unaffected eyes of 26 CCSC patients receiving half-dose PDT, and 40 eyes of 20 healthy gender- and age-matched subjects were retrospectively enrolled. Proportion of total areas of flow signal voids (FSV, %) in CC level of OCTA were mainly assessments in both eyes of the CCSC patients at baseline and repeated in multiple sections at 1-week, 1-month, 3-month and 6-month intervals after PDT. In addition, CC patterns in response to PDT at early stage and their subsequent morphologic changes were qualitatively documented using OCTA. Results: For affected eyes, significant decrease in FSV was found at 6-m follow-up than 1-m follow-up (p=0.036). Comparing to normal control eyes, FSV in affected eyes was significantly higher at 1-m, 3-m and 6-m follow-up (p<0.05 for all), while FSV in unaffected eyes was significantly higher at baseline, 1-w, 1-m and 3-m follow-up (p<0.05 for all). Three CC patterns of early response to PDT can be identified, including signs of recovery with more even flow signals, transient appearance of worsen ischemia and secondary neovascularization within CC level. Conclusion: Abnormal CC flow attenuation remained in completely resolved eyes of CCSC patients treated with half-dose PDT. Key Words: Chronic; Central Serous Chorioretinopathy; Optical Coherence Tomography Angiography; Photodynamic Therapy