The time-delay characteristic and effective bandwidth of semiconductor lasers produced by dual modulation of external optical injection and feedback are numerically and experimentally investigated. The experimental results show that the dual-modulated laser system has large bandwidth, and the time-delay characteristic is weakened compared with the single-modulated laser system. The experimental results have been compared to verify the obtained numerical results, indicating that the proposed scheme can improve the security performance of chaotic laser-based secure communication. Besides, more effective bandwidth and less time-delay characteristic can be obtained in the negative frequency-detuning region. The delay characteristic suppression will deteriorate in the positive frequency-detuning region.