Automatic reconstruction of unknown three-dimensional (3D) objects is one of the classical research in machine vision, which is widely used in industrial inspection, robot localization and navigation, reverse engineering, and cultural relic restoration etc. A new approach of reconstructing unknown 3D models automatically is proposed. The new algorithm incorporates the visual region of the monocular laser-vision system with the limit visual surface of unknown model and selects the suitability of viewpoints as the NBV on scanning coverage. The limit visual surface is modeled by the known surface data obtained from initial view and is used to predict the maximal unknown object surface information. Then the next view visibility is determined, correspondingly the visual rotation angle and translation zones are obtained. And the position which can obtain the maximal visual surface area in the visibility zone is selected as the next best view position. The experimental results show that the method is effective in practical implementation.