A lane departure warning system includes a front camera generating front image information of a vehicle. A speaker outputs a departure warning message, and a screen displays an image including user interface objects. A touch detector generates touch information by detecting a user's touch on the screen. A controller recognizes lanes at both sides of a current driving road by using the front image information, sets first and second warning lines based on the lanes, and controls the speaker to output the departure warning message if the vehicle reaches one of the first and second warning lines. The controller calculates a touch operation time by using the touch information and changes the first and second warning lines to third and fourth warning liens if the touch operation time is greater than a first reference time. A distance between the third and fourth warning lines is less than a distance between the first and second warning lines.