Shotcretes, rockbolts, and steel supports are used as a primary lining for NATM tunnels. However, the H-beam steel ribs have many disadvantages. Therefore, lattice girders are developed in Europe to overcome the disadvantage of the H-beam steel ribs.The lattice girder is a triangular shape welded with steel rods and is a light-weight support system which enable fast and easy installation of porepolling. Another major advantage of a lattice girder is the good bonding with shotcrete.Laboratory bending tests for the lattice girder are done in this study to know the effect of the material and the size of the lattice girder on the performance of the girder. General steel with the 12mm diameter of the spider are used for the experiments instead of the regular lattice girder made with special steel having 10mm diameter of the spider.Lattice girders made with general steel show 1.5 times less strength compared to that of special steel, whereas the 12mm diameter of the spider show 1.5 times higher strength than that of the 10mm diameter of the spider.