1. A large-range-first cross-camera visual target re-identification method, characterized in that said method comprises: step S 1 : obtaining initial single-camera tracks of targets; step S 2 : calculating a piecewise major color spectrum histogram feature of each track and obtaining a track feature representation; step S 3 : obtaining a calculation formula for the similarity between any two tracks by using a minimum uncertainty method so as to obtain the similarity between any two tracks; step S 4 : performing global data association on all the tracks by using a maximum posterior probability method to obtain a cross-camera tracking result.