The embodiment of the invention provides an image acquisition method and system which are used for solving the technical problem that in the prior art, a target object cannot be monitored precisely inreal time. The method comprises the steps that the accumulated occurrence numbers of characteristic elements in various unit areas of a video picture acquired by a gun camera in a predetermined timeare determined; the characteristic unit area in which the accumulated occurrence number exceeds a first threshold value is screened out from all the unit areas, wherein the first threshold value is larger than or equal to 0; at least one active area is determined according to the screened-out characteristic unit area, and first coordinate parameters of the at least one active areas in a gun cameraimage coordinate system are determined; second coordinate parameters corresponding to the first coordinate parameters of the at least one active area on a dome camera image coordinate system are determined according to the mapping relation between gun camera image coordinates and dome camera image coordinates, so that a dome camera conducts image acquisition on scenes corresponding to the at least one active area according to the second coordinate parameters.