A steel cord containing a core layer and an sheath layer, the core layer containing a plurality of core wires with a number of n and the sheath layer comprises a plurality of sheath wires with a number of m, and the steel cord has a flat cross-section with a major axis and a minor axis, the flat cross-section has a flat ratio being the ratio of the length of the major axis and the length of the minor axis, the flat ratio is more than 1.2, the steel cord has a breaking load being BLcord, the core wires and the sheath wires have a sum breaking load being Sum BLwires when the core wires and the sheath wires are un-twisted from the steel cord, BLcord and Sum BLwires satisfies the following formula: BLcord/Sum BLwires>96%. The steel cord has higher breaking load.