The utility model refers to a water color pen;especially a water color pen that is free of replacing the core frequently caused by the requirement of different lines and can draw out pictures of three-dimension effect.The new water color pen includes the pen tube and the water color core inside it. An air pressurizing mechanism is provided on upper end of the pen tube and a small round cone is extended into the lower end with an ink hole in central of the round cone.Said pen point of the pen core is inside the ink hole of the small round cone and does not protrude outside the tube; an air hole is cut on pen point of the pen core. Said air pressurizing mechanism is a plastics airbag fitted over upper end of the tube. Said air pressurizing mechanism is a push-and-pull piston assembled on upper end of the tube. Said pen core includes an ink tube body, a sealing plug and a sponge pen point. The shaping picture is more realistic and full of three-dimension effect owing that the ink jet type drawing is adopted. It is not required to replace the pen core to meet the drawing demand of different lines, which greatly saves the cost as well as the replacing procedure.