The advantages and disadvantages of various on-line icing-monitoring methods for power supply line are analyzed. The principle of icing-monitoring based on inclination and sag method is introduced, and the effect of icing on wire stiffness is analyzed, and the paper amends wire elasticity coefficient using inclination sag method to calculate the weight of icing. The on-line icing-monitoring device of power supply line based on temperature and inclination measurement is designed in this paper, and reducing power loss, ensuring data accuracy and improving the operation stability are mainly taken into account. The temperature and inclination data monitored combine with video and meteorological information acquired by base station can timely and comprehensively reflect power supply line icing state. It takes an active part in power grid operating safely in icing areas.