Bending strength is a critical property of cross laminated timber (CLT) in structural applications, especially in floor of multi-story buildings. Therefore, this study was targeted to evaluate bending strength of CLT made out of poplar (populous alba). Polyurethane adhesive was used for constructing of CLT (300 g/m2). The thickness of planks was used in this study was 16 mm. The results have indicated that modulus of rupture (MOR) and modulus of elasticity (MOE) of CLT with 45o alternating transverse layer were increased 14 and 15%, respectively in comparison with 90o layers. Also, modulus of rupture (MOR) and modulus of elasticity (MOE) of CLT consist of layers with 4cm in width were increased 14 and 5%, respectively in comparison with layers 9cm in width. The results concluded that by layers with lower width, and also 45o alternating layer configuration could be constructed CLT from fast growing trees such as poplar with a considerable bending strength.