The invention relates to a broadband radiation unit and an antenna. The broadband radiation unit includes a balun and four radiation arms, wherein the radiation arms are connected to the balun, and are arranged around the center line of the balun in the circumferential direction; a gap is arranged between terminals of the adjacent two radiation arms, and a slit is formed in the radiation plane ofat least one radiation arm; and the setting direction of the slit is corresponding to the setting direction of the radiation arm on which the slit is located. As the slit is formed in the radiation arm, the broadband radiation unit can obviously improve the convergence of the medium high frequency half-power beam width in a high and low frequency nested scheme; as a metal boundary is not demandedto set between the non-nested high frequency radiation unit and the low frequency radiation unit, the boundary of the high frequency radiation unit can be simplified; and adding of the high and low frequency debugging piece is not demanded to add, thus avoiding the adverse effect on the low frequency circuit and the radiation index by the high and low frequency debugging piece.