A novel direct dual Z-scheme g-C3N4/Bi2WO6/AgI (CBA) ternary heterojunction photocatalyst was fabricated through the hydrothermal reaction and a succedent in-situ precipitation route for the first time. Systematic studies showed that the 20% AgI and 60% g-C3N4 co-modified Bi2WO6 presented the highest photocatalytic performance, achieving 91.13% removal efficiency of tetracycline within 60 min, which was 10.04 times that of pure Bi2WO6. The enhanced photocatalytic performance mainly derived from the co-effects of Bi2WO6, g-C3N4 and AgI and could be summarized as following: i) The g-C3N4 nanosheets could be used as carriers for dispersion of Bi2WO6 and AgI nanoparticles, preventing their agglomeration; ii) The addition of g-C3N4 and AgI could promote the light absorption, resulting in the strengthened light harvesting ability; iii) The intimate contact of Bi2WO6, g-C3N4, and AgI favored the separation and transfer of photogenerated carriers. Further analysis demonstrated that the path of photogenerated electrons moved exhibited a direct dual Z-scheme pattern in ternary heterojunction, which not only fulfilled the efficient spatial separation of photogenerated electron-hole pairs but also endowed the composites with strong redox capability, thereby boosting the photodegradation efficiency of CBA composite. This work opens a new strategy to constructing multi-component Z-scheme photocatalytic system for environmental decontamination.