The invention provides a dual-moving-blade thread trimming device and method of a sewing machine. The dual-moving-blade thread trimming device of the sewing machine comprises a first moving blade, a second moving blade, an electronic control module, a detecting sensor, a sensed piece which is fixed to the second moving blade and can be sensed by the detecting sensor, a first driving source, a second driving source, a first driving assembly and a second driving assembly. The first driving source is connected with the first moving blade through the first driving assembly. The second driving source is connected with the second moving blade through the second driving assembly. The detecting sensor, the first driving source and the second driving source are connected with the electronic controlmodule. The electronic control module precisely controls the action stopping time point of the second driving source according to the changes of output signals of the detecting sensor when the secondmoving blade moves forwards so as to precisely control the second limit position of the second moving blade moving forwards and make the second moving blade move forwards to a thread cutting point, and the thread cutting effect of short thread residues can be stably realized; no linkage exists in the movements between the first moving blade and the second moving blade, and the device is easy to obtain.