Embodiments of the present disclosure provide a method and system for positioning a robot and adjusting a posture. The method may include obtaining a first image and a second image of a target object. The first image may be captured using an image capturing apparatus, and the second image may be captured using a medical imaging device. The method may also include determining at least one target region corresponding to at least one target portion of the target object from the first image. The at least one target portion may be less affected by physiological motions than other portions. The method may further include determining positioning information of the robot based on the at least one target region and the second image.