Method and system for demonstrating a function of a vehicle-mounted heads up display are disclosed. The method includes setting a projection region for displaying a first image, obtaining relative position and relative size relationships between the projection region and the virtual display region, projecting the first image in the projection region, capturing a second image of the first image, generating a virtual recognition region in the second image, determining whether an object in the second image is located within the virtual recognition region, and determining, in a case that the object is located within the virtual recognition region, a first position of the object within the virtual recognition region, determining, based on the first position, a display position of a virtual marker representative of the object within the virtual display region, and displaying the virtual marker at the display position within the virtual display region.