AbstractWheat straws were split longitudinally using a specially designed straw splitter. Oriented structural boards made from the split straw strands were fabricated with polymeric diphenylmethane diisocyanate (pMDI) resin. The effects of the split straw strand length, resin content, and panel density on the properties of oriented structural straw board (OSSB) were investigated. Dimensional analysis showed that the average length of split straw strands after screening of the fines was 83.74 mm. More than 70% of the straw strands were in the range of 50 to 90 mm in length. The bending properties of the OSSB were highly related to the length of the split straws. The modulus of rupture (MOR) and modulus of elasticity (MOE) increased significantly as the split straw length was increased, particularly from 11 mm to 45 mm. The preferable length of the split straw was at least 40 mm to satisfy the MOE requirements. For a given pMDI content level, the internal bond (IB) strength increased linearly with an increase in panel density, which is consistent with previous results for wood-based panels. This study demonstrated that satisfactory OSSB can be made using approximately 3% pMDI at an average panel density of 640 kg/m³ to comply with the North American OSB products standard.