A new method of parameter reconstruction for fiber gratings from desired time-delay characteristics is presented by genetic algorithm (GA) in conjunction with the transfer matrix method in this paper. The objective function in this method is time-delay of fiber gratings, and the individuals of population are the parameters of fiber gratings, including the grating length, refractive index modulation, grating period and grating chirp. The optimal solution is obtained through many generations calculation. The real-coded genetic algorithm is used for parameter reconstruction of uniform, chirped and apodized fiber gratings. Numerical simulating results show that the method is very effective for parameter reconstruction of fiber gratings according to desired time-delay characteristics. An apodized chirped fiber grating is reconstructed from an ideally linear time-delay characteristics whose slope is 100 ps/nm, maximum time-delay is 300 ps and center wavelength is 1555.2 nm. The method proposed can effectively obtain the parameters of fiber gratings from time-delay figures, and can be applied in the design of optically controlled phased-array antennas based on the time-delay characteristics of fiber gratings.