The invention discloses a light asynchronous sampling signal measurement method and system. The system comprises a light source, a signal light path, a reference light path and a detection device, wherein the light source can output two pules of different repetition frequencies, and the light asynchronous sampling signal measurement is realized. According to the invention, the light asynchronous sampling signal measurement can be realized by one pulse light source, and the complexity and the cost of the system are lowered.