1. An apparatus for acquiring an X-ray image, the apparatus comprising: an X-ray source which generates X-rays and irradiates the X-rays onto an object; a detector which acquires the X-ray image being generated when the X-rays penetrate the object; and a processor which generates a source optimal parameter and a detector optimal parameter based on a characteristic of the object, and controls the X-ray source and the detector based on the generated source optimal parameter and the generated detector optimal parameter, respectively, wherein the processor generates the source optimal parameter and the detector optimal parameter by: simulating a plurality of parameters related to the X-ray source and the detector, and selecting the source optimal parameter and the detector optimal parameter from the plurality of parameters.