Laminated Veneer Lumber (LVL) is a kind of wood engineering product and commonly used as joists in timber construction. Holes in joists used as part of a floor system within a building are often required to allow services to pass through. Cutting holes can initiate cracks that can propagate when joists are loaded, and fracture will occur. This paper analyzes the failure mechanism of LVL joists with holes and reinforcement methods with nailed-plywood around holes. Experiments showed that joists with a hole have a dramatically reduce in carrying capacity. And the plywood worked effectively for reinforcing LVL joists. Experiments also showed that the carrying capacity increasing with increasing of the thickness of plywood and the quantity of nails.