According to the confusion effect of processing route drawing, few sampling points and contradiction between timing accuracy and system fluency of Windows system in high-speed CNC real-time plotting process, this paper presents a method based on Windows environment to achieve real-time plotting goal of the machining contour in high-speed CNC laser cutting process by pretreating G codes and interpolation algorithm improvement. Experimental research was implemented and this method has already been successfully applied to practical production. Comparing to traditional real-time plotting method, this method can not only achieve faster real-time plotting, but also ensure accurate graphic drawing quality and meet the demand of practical circumstances. This method, put forward by the author in addressing real-time plotting problem of laser cutting, can be equally applied to other two-dimensional high-speed cutting occasions.