The construction methods and engineering experience of the three construction steps of the rock anchor beam of Xiaowan underground powerhouse, i. e., rock anchor beam excavation, pulled/stressed rock anchor construction and concrete casting, are briefly presented. For the excavation of the critical part of the rock anchor beam of Xiaowan underground powerhouse, the shotholes are drilled by pneumatic drills, steel pipe scaffolds are erected so as to be used as working platforms, the construction accuracy is controlled within the designed limits, the spacing of the shotholes generally is 32cm, the linear charging density is 75.8k/m and is appropriately reduced in accordance with the actual conditions where the geology is poor. As a result, a semihole ratio of 98% is achieved, the sockets have no cracks, the average overbreak is controlled below 8.9cm, the parameters of the blasting vibrations meet the requirements of the related standards and the construction quality reaches "excellent" standard. Furthermore, the construction methods and accuracy control methods for the rock anchors of the rock anchor beam and the concrete casting methods are described in detail.