The invention provides an ultra-wide band ladder-like FM/CW laser speed measurement system based on a double-parallel MZM, and belongs to the technical field of laser speed measurement. The problem is solved that when a traditional sawtooth wave modulation FM/CW laser radar measures a speed, due to distance-speed coupling, a moving speed of a measured mobile target cannot be obtained through a single time of measurement and a single time of calculation. In the ultra-wide band ladder-like FM/CW laser speed measurement system based on the double-parallel MZM, according to a modulation end, a single frequency continuous laser source, the double-parallel MZM and an optical fiber amplifier are adopted to constitute an optical fiber loop to jointly constitute a signal regulation system along with an adjustable F-P optical fiber filter so as to generate a light signal with a ladder-like frequency modulation function, the light signal is subjected to beam splitting through a number two 1*2 beam splitter, one beam of signal light and one beam of local light are obtained, the local light is reflected through a target after entering the target, a digital signal processor processes the received signal light and the local light which carries measured mobile target information, and thus the moving speed of the measured target is obtained. The ultra-wide band ladder-like FM/CW laser speed measurement system based on the double-parallel MZM is mainly used for measuring the moving speed of the measured target.