Influence of butt joint gap in ultra-long laminated bamboo sliver lumber（LBSL）from Moso bamboo（Phyllostachys pubescen）was studied.The effects of gap depth and position were analyzed by determining the LBSL bending performance.The results showed that LBSL bending performance decreased with the gap on the surface gradually deepened.The butt joint gap had no obvious effect on the LBSL bending performance only when the gap depth was less than 5% of the total lumber thickness.The closer of the gap position near the lumber core,the less influence of the gap position had on LBSL bending performance.It was concluded that for making LBSL,butt joint gap should be avoided in forming process,especially no gap should be allowed on the surface.