This study describes a simple head mounted display(HMD) viewing system for an unmanned construction system(UCS) and an assessment of the work efficiency using the HMD system. The deployment of a UCS is a significant problem because majority of the construction machines are not compatible with remote operation. In this study, focusing on the deployment problem regarding the viewing system of a UCS, we developed a simple HMD type viewing system. The HMD system provides the visual information so that images are projected on the HMD in the same arrangement as conventional LCD monitor systems. The HMD system of a hydraulic excavator was tested with respect to work efficiency in comparison with a conventional LCD system using a model task that simulates the excavation and transportation of soil. Experimental results of the model task indicate that the working efficiency of the HMD system was improved compared to the conventional LCD system.