The interactions between AC and DC systems in the steady-state condition of power systems are investigated. Through a sensitivity analysis， the influence of DC control parameters on the operation of AC/DC systems and that of AC control parameters on other AC parameters with the DC system existing are discussed. The sensitivity matrices and the influence factors between AC and DC systems are analyzed from various points of view. The sensitivity analysis made in this paper is expected to be of practical significance in such problems as load flow control， parameter regulation， voltage estimation， etc.