The present invention discloses a fast scan-type panoramic image synthesis method and device. The device includes: simultaneously acquiring two original images of the same angle of view, wherein one is an exposure-locked image and the other is a non-exposure-locked image; performing HDR processing on the two simultaneously acquired original images by using the exposure-locked image as a reference image to obtain an HDR processed outcome image; performing exposure compensation on the HDR processed outcome image of the current frame based on the temporary panoramic outcome image of the previous frame; and performing image fusion and synthesis according to the temporary panoramic outcome image of the previous frame and the exposure compensated HDR processed outcome image of the current frame to generate a new temporary panoramic outcome image of the current frame. The present invention can effectively restore lost details in areas of over-exposure and under-exposure in the original images, thereby avoiding the issue of detail loss in a panoramic image caused by locked exposure.