The invention discloses a soft pen drawing method and device based on a touch screen, and the width of a drawing line is adjusted through the size of speed. According to a key point algorithm, a route is optimized through a Bezier curve, and a drawing line segment is cured in the fitting and optimizing route in an incremental mode. According to the soft pen drawing method and device based on the touch screen, drawing is conducted by simulating a soft pen, the trueness of drawing an image is high through the soft pen drawing method, the real-time performance of display is high, the whole drawing process is very true, and a user feels good in the drawing process.