A movable carrier auxiliary system includes at least one optical image capturing system disposed on a movable carrier, at least one warning module, and at least one displaying device. The optical image capturing system includes an image capturing module and an operation module, and has at least one lens group including at least two lenses having refractive power. The image capturing module captures and produces an environmental image surrounding the movable carrier. The operation module electrically connected to the image capturing module detects at least one lane marking in the environmental image to generate a detecting signal. The warning module electrically connected to the operation module receives the detecting signal to determine whether a moving direction of the movable carrier deviates from a lane, and generate a warning signal when the moving direction deviates from the lane. The displaying device electrically connected to the warning module displays the warning signal.