Abstract: For galloping of iced bundled conductors, the touching of phase lines is taken as the criterion in engineering practice. The criterion equation was derived from dynamical equations, indicating that coupling of aero dynamical forces may result in extremely small aero dynamical torsional rigidity of iced bundled conductors, which causes the galloping of iced bundled conductors. The difference between the conclusion and existing galloping theory is that galloping is not dynamical unstability and galloping of iced bundled conductors may occur under steady dynamical condition.