The invention belongs to the technical field of target extraction, particularly relates to a color-based writing trace extraction method, system and device under a complex background, and aims to solve the problems that an existing extraction method is incomplete in writing trace extraction and high in image quality requirement, and writing traces with changed colors cannot be extracted under a complex environment. The method comprises the steps of converting a to-be-detected image containing a to-be-detected writing trace into an HSV color space, selecting seed points based on the HSV color space, and dynamically obtaining pixel points on an edge image from the seed points to serve as newly-added to-be-traversed points; and based on the seed points and newly added points to be traversed,obtaining a pixel set of writing traces to be detected through image refinement. According to the method, the connectivity of the correction trace can be enhanced, and the correction trace can be effectively extracted in a complex scene; meanwhile, the conditions of newly-added points to be traversed are strictly set, the outline of the writing trace can be effectively controlled, excessive noiseis prevented from being introduced, and subsequent processing is facilitated.