The hydraulic excavators are mainly applied for excavating, public works, quarrying, etc. In some of the construction site, however, they are used for crane works of relatively light materials, although the crane works by the hydraulic excavators are forbidden by law due to the safety reasons. The major construction equipment companies in forward countries have been developing the new systems, e.g. crane works by the hydraulic excavators, and they are working in the construction site. Therefore, the new system of crane works by the hydraulic excavators should be developed for the domestic construction site in order to prevent the accident. In this paper, the fundamental study and experiment are accomplished for the crane system application on the hydraulic excavators.