The width of the mainlobe generated by the conventional broad-band beamforming method varies with frequency or beam point-ing angle, and is affected by the number of array elements. In this paper, a frequency and steering invariant beamforming method based on compressed sensing(CSFSIB) is proposed. In this method, the array elements are extended virtually firstly. Then the sparse signal was reconstructed by compressed sensing(CS) recovery algorithm, the Second-order cone programming(SOCP) method is used to calculate the weighted vector and optimize the steering-invariant beamforming(SIB). Finally, frequency-invariant beamforming is designed based on inverse Fourier transform(IFT). The simulation results indicate that the proposed method can reduce the sidelobe level and save the number of array elements while keeping the mainlobe width constant.