A monocular vision-based method for measuring displacement and trajectory of planar motion. In this method, a sequence image of a motion of a high-contrast feature mark fixed on a moving plane to be measured is collected using a camera. A sub-pixel coordinate of a feature edge of a linear motion of the sequence in an X direction and a Y direction is extracted using a sub-pixel edge detection method, and the sub-pixel coordinate is converted into a corresponding world coordinate. The world coordinate of the feature edge is fitted based on a least squares principle to obtain a straight line of the feature edge to realize decoupling measurement of a displacement in the X direction and the Y direction. The planar motion trajectory is obtained through measuring the displacement in the X direction and the Y direction.