Abstarct: With the increasing development of urban areas and the need for communities to urban transport infrastructure such as tunnels, water tunnels, and other underground structures need to be constructed in these areas. Mechanized tunnelling by Tunnel Boring Machines (TBM) is one of tunnel excavation methods. In order to encounter the settlement, maintain the stability of excavated space, preventing the entry of water into the tunnel and etc the tunnel excavation is done simultaneous with installing concrete segments. Due to differences between excavating diameter and precast concrete components diameter, it’s necessary to filling the gap between those. This operation is named “Contact grouting”. filler material has usually pumped slurry type into the gap. This thesis has found suitable mix design contact grouting in Auxiliary Channel Tunnel is Aboozar. Cement, sand, bentonite and water are main material of contact grouting. Stability, bleeding, shrinkage and efficiency are more important factors in grout providing. In order to reach to the suitable mix design, it has provided 42 samples with different weight ratio of grout material. For each sample, it has taken 24 hours and 7 days Uniaxial Compressive Strength (UCS) test and it has determined grout bleeding and shrinkage percent. Finally it has exhibited suitable mix design for auxiliary channel of Aboozar tunnel. It has determined suitable mix design material as 340, 10, 1100 and 490 kg per cubic meter for cement, bentonite, sand, and water, respectively.