Asymmetrical apodization method is introduced to optimize chirped fiber Bragg gratings based on the analysis of its reflectivity spectrum and time delay response. The optimization effects for grating parameters, by the optimum apodization ratio of the symmetrical apodization, the left-shifted and right-shifted asymmetrical apodization methods and different apodization functions, are analyzed and compared. The results show that, compared with symmetrical apodization method, the asymmetrical apodization method can avoid the disadvantage of the former method that widens the reflectivity bandwidth by reduction of apodization ratio, which meanwhile increases the time delay ripple. The left-shifted apodization method can reduced the time delay ripple by 43.5%, adjacent with the experimental result of 39.9%, while the refectivity spectrum is nearly unchanged. Furthermore, better performance can be obtained with super-Gaussian function on left-side and Hamming function on right-side of chirped fiber Bragg gratings than Hamming function on both sides. The plain part of the reflectivity ripple is reduced 89.3%, as well as fitting error of group delay ripple 16.7%.