Objective To investigate the basic mechanism of venous flow in reverseflow island flap. Methods Recent relevant literature on the mechanism of venous reverse flow in reverseflow island flap wereextensively reviewed. Results The mechanism of venous reverse flow was a multifactorial phenomenon. “Communicating and collateral by pass route” and “incompetent valve route” were two theories. Conclusion The two routes of venous reverse flow in reverse-flow island flap coexistand complement each other.