This paper describes an operational support system to simplify removing objects from a building structure in demolition work using dual-arm construction machinery. An operator cannot recognize the manipulator movement visually when a target object is strongly restrained in an unmovable environment, so the operator continues large lever-operations for a while after the object has been removed. This could lead to a collision against the surrounding environment. An operational support in construction machinery filed requires the compatibility among efficiency, quality, and safety and the commonality among various operator skill levels. The proposed support system thus identifies the moment when an object has been removed and cancels any operational inputs to ensure safety work when generating intensive force applied to a manipulator, focusing only on the common physical phenomena. An object-removal flag is defined as a situation where force applied to the end-point of a manipulator decrease rapidly in which lever operation and hand load are detected. Demolition experiments are conducted using a hydraulic dual arm system. Result indicates that the displacement of end-effector after removal and the number of error contacts are decreased while decreasing time consumption.