Abstract An experimental apparatus for methane and air mixture vented explosion in connected vessels has been set up. A series of experiments have been performed to analyze the characteristics of external overpressure induced by vented explosion in linked vessels. Multi-peak and oscillation are the main characteristics of external overpressure. The external explosion strength caused by vented explosion in linked vessels is much higher than that in a single vessel. The external explosion intensity increases with connecting pipe length. The external explosion strength associated with the flame propagating from the small vessel to the big vessel is much higher than that in reverse direction. The study is significant to reveal the essential characteristic of explosion venting process and improve basic theory of gas explosion venting. And the research results will provide important references for safety design of gas explosion venting and personnel safety protection.