The present invention relates to the field of communication transmission, and in particular, to a method for generating a probe pulse and a coherent optical time domain reflectometer. The coherent optical time domain reflectometer includes: a control unit, configured to generate a first pulse signal and a second pulse signal which have a same period T, where the second pulse signal lags behind the first pulse signal, and T satisfies T≧t+2L/C; a driving unit, configured to generate a frequency change driving signal according to the first pulse signal; a continuous light laser device, configured to generate, as driven by the frequency change driving signal, continuous light having a changing frequency and an unchanging frequency spectrum width; and a probe pulse generating unit, configured to modulate the continuous light according to the second pulse signal to generate a probe pulse.