An electric cabinet with a heat dissipation system is provided. The electric cabinet includes an body and a plurality of electric boards amounted in rows and arranged vertically in the body. The heat dissipation system includes: an air inlet and an air outlet respectively located on a lower surface and a higher surface of the body; a fan having fan blades arranged horizontally amounted between two of the electric boards for guiding the air to flow from the air inlet to the air outlet; and a plurality of air-cooling devices, each is amounted on sides of the body and designated with cooling one of the electric boards, wherein at least one of the air-cooling devices is amounted to be higher than the horizontal blades of the fan.