This research was concerned with study of failure strength of natural fiber reinforced composites. Tensile-shear tests were carried out with single-lap-adhesive-joined specimens consisting of polyester lap and composite lap. Composites were manufactured using the polyester as matrix and bamboo natural fiber layer as reinforcement. Two types of specimens with different reinforcement positions were tested to evaluate the failure strength of adhesive-single-lap-joined natural fiber reinforced composites. The test results were presented by tensile-shear strength graph comparing with finite element analysis. The failure mechanism was discussed in order to explain the lower tensile-shear strength of composite, and effect of position of bamboo natural fiber layer on the failure strength properties were explained.