Different nonlinear dynamic behaviors of the distributed feedback semiconductor laser (DFB-SL) subjected to external optical feedback have been investigated experimentally and theoretically. The experimental results show that DFB-SL can exhibit rich nonlinear dynamic behaviors such as stable state,one-period,double-period,multi-period and chaos under different feedback strengths. For the laser operating at the series of periodic states,there are obvious characteristic frequency peaks in corresponding optical spectra and power spectra while the background noise is very low. Moreover,after increasing the feedback strength to a certain level,the coherence collapse will happen due to the strong mode competition of DFB-SL,and 10 GHz broadband chaos can be obtained experimentally. In addition,the numerical simulations are executed,and the results agree well with the experimental observations. The simulations also indicate that the feedback strength is a key parameter for controlling nonlinear dynamic behaviors of DFB-SL.