In order to improve the passband flatness and 3 dB modulation bandwidth of the distributed feedback (DFB) lasers, we study the relationship between the device parameters (such as grating coupling coefficient, cavity length and electrode ratio) and the frequency response of 1 st and 2 nd order grating push-pull modulated DFB lasers by using one-dimensional traveling wave model. The parameters used in the simulated model are extracted from the photoelectric characteristics of the actual devices. The simulated results show that, for the DFB lasers with 1 st order grating structure, the push-pull modulation bandwidth is 12 GHz larger than the single-electrode direct modulation bandwidth at the appropriate grating coupling coefficient, cavity length and electrode ratio. For the DFB lasers with 2 nd order grating structure, the push-pull modulation bandwidth is 40 GHz larger than the single-electrode direct modulation bandwidth. Besides, the passband flatness of the 1 st order and 2 nd order grating push-pull modulated lasers is much better than that of the ordinary direct modulation lasers. In addition, the results of the experiments show a substantial increase of the bandwidth with push-pull modulation, even for general design of active region.