To address the key challenges of high chemical oxygen demand (COD), intense color, and poor biodegradability commonly found in the biological effluent of actual pharmaceutical wastewater, an electrochemical-ultraviolet-ozone(EC-UV-O3) ternary coupling advanced oxidation system was developed, and its treatment performance and underlying mechanisms were systematically investigated. The performance of three individual systems (UV,O3,EC), three binary coupling systems (O3-UV, EC-UV, EC-O3), and the EC-UV-O3 ternary system were compared. The results reveal that the EC-UV-O3 system achieves the highest treatment efficiency, COD removal rate reaches 91.1% in this system, color is completely eliminated within 40 min, and the BOD5/COD ratio increases from 0.11 to 0.59, indicating a marked improvement in biodegradability. Optimization results indicate that the system achieves the best overall performance at an electric current density of 30 mA/cm2, an O3 dosage ratio of 1.0 (mO3/mCOD), an electrode spacing of 1.0 cm, and an initial pH of 7.2, balancing high pollutant removal efficiency with energy consumption. Mechanistic analyses confirm that the enhanced generation of reactive oxygen species (ROS), including ·OH and 1O2, is the primary factor driving the improved organic pollutant removal in the EC-UV-O3 system. This study provides certain data support and theoretical basis for the engineering application of the EC-UV-O3 process in the advanced treatment of actual pharmaceutical wastewater.