1. A computer-implemented method for adjusting image parameters of cameras, comprising: (a) obtaining image parameters of each of the cameras from a storage system of each of the cameras, and adjusting an image quality of a captured image of each of the cameras according to the image parameters; (b) determining if there are disqualified cameras whose image parameters need to be adjusted according to the image quality of the captured image of each of the cameras; (c) processing the captured image of each of qualified cameras whose image parameters do not need to be adjusted, and outputting a processed image of each of the qualified cameras on a display; or (d) determining if the image parameters of each of the disqualified cameras are adjusted by the computer through a network; (e) updating the image parameters by each of the disqualified cameras itself if the image parameters of each of the disqualified cameras are not adjusted by the computer through the network, and returning to step (a); (f) determining if the image parameters of each of the disqualified cameras have been adjusted using a broadcast mode under the condition that the image parameters of each of the disqualified cameras are adjusted by the computer through the network; and (g) updating the image parameters of each of the disqualified cameras using the broadcast mode or a non-broadcast mode with user-defined values, and returning to step (a); wherein the image parameters of each of the cameras are stored in a default image parameter area of the storage system of each of the cameras; wherein step (f) comprises: determining that the image parameters of the disqualified cameras have been adjusted using a non-broadcast mode if a broadcast key of each of the disqualified cameras is equal to zero; and determining that the image parameters of the disqualified cameras have been adjusted using the broadcast mode if the broadcast key of each of the disqualified cameras is equal to one; wherein step (g) comprises: updating the image parameters in the default image parameter area of the storage system of each of the disqualified cameras in succession with the user-defined values using the non-broadcast mode through the network if the broadcast key of the disqualified camera is equal to zero; and updating the image parameters in the default image parameter area of the storage system of each of the disqualified cameras synchronized with the user-defined values using the broadcast mode through the network if the broadcast key of the disqualified camera is equal to one.