The combination of camera and 2D laser-rangefinder has been widely used in the fields of surveying, pilotless and robot. Extrinsic calibration between the two sensors is a prerequisite for fusing the texture information from images and depth information from the laser. To tackle this problem, a method of calibrating the extrinsic parameters between a camera and a 2D laser-rangefinder is proposed. This method establishes three geometric constraints between the laser scanning line and the V-shaped chessboard plane, including point to plane constraint, line to plane constrain and point to line constraint. The extrinsic parameters can be solved and optimized by redundant geometric constrains which help mitigate the impacts of noises in the laser points and image data. Experiments show that the proposed algorithm achieves higher accuracy and robustness than previous methods. And a quantitative evaluation criteria of the extrinsic parameters is proposed by calculating the distance between the intersecting point of the laser lines and the V-shaped chessboard line.