The primary objective of this paper is to put forward a recommended equivalent calculated length coefficient for global stability analysis of the mono-overhanging steel beam applied widely in the steel building construction. The formulas of the total potential energy of the mono-overhanging beam are deduced firstly. Then the formula of the critical moment of the global stability of the mono-overhanging beam is obtained. By introducing the equivalent calculated length coefficient of the global stability and finding out the major factors which affected it, the formula of the coefficient is deduced. This formula includes two kinds of load acted on different position and it can make the global stability analysis of the mono-overhanging steel beam more convenient.