Abstract: Design of a constant beamwidth beam-former (CBB) based on Chirped Z Transform (CZT) are proposed: within every frequency sub-band,assuming that weighting coefficient sequences of beams oriented to different directions are the same.Then it can be concluded from the deduction that the sequences in all sub-bands have the same spectrum, but a scale relationship is satisfied on the frequency axes.The scale is equal to the ratio of the reference frequency to the central frequency in each sub-band.According to the design ideas of CBB,the CBB method based on CZT with Invariable Aperture (CZTIA) and the one with Variable Aperture (CZTVA) are presented.It is the same in these two methods that the weighting sequence of the reference frequency is obtained firstly,and then by use of CZT with different parameters values,the spectrums of weighting sequences in all sub-bands can be calculated,and finally they can be obtained by inverse fast Fourier transform (IFFT).The validity of these conclusions is validated with computer simulations.