Abstarct: In some parts of constructing east-west road tunnel of line 7 Tehran subway, the excavating machine passes from the top of the Aboozar’s wastewater conveyance tunnel with distance of 2.25 m. In this study, FLAC 3D is used in order to study the interaction between the two tunnels. The modeling results show that after excavating subway tunnel, lining system of Aboozar tunnel will be moving upward due to the increasing plastic zones and stress relaxation. In this rate of displacement, the crown of Aboozar tunnel will shift upward in rate of 7.3 mm and tunnel invert will shift upward in rate of 6.6 mm. This rate displacement creates the internal tensile force in crown of the tunnel in rate of 1266 KN which is more than designed allowable amount in concrete lining of Aboozar tunnel. So some strategies should be suggested in order to reduce the interaction between two tunnels. Proposed strategies include controlling face pressure, grouting pressure behind concrete lining, subway tunnel over-excavation and soil improvement between two tunnels. In conducted modeling it has specified that, by increasing face pressure and grouting pressure behind concrete lining of subway tunnel, created tensile force in crown of tunnel will reduce which will cause the lining system instability, but these changes due to increasing face pressures will be lesser in compared with changes due to increasing grouting pressure behind the concrete lining. With reviewing over-excavation, it has specified that by increasing the subway tunnel over-excavation with respect to increasing convergence of soil around the tunnel, created tensile force will be increased in crown of the tunnel. In order to evaluat the effect of soil improvement between two tunnels on their interaction, two models have created. in the first case, soil lying between two tunnels until the walls of Aboozar tunnel has improved and in second case all soil has improved around Aboozar tunnel. Modeling results indicate that changes in axial forces and bending moments are almost identical in both cases. It was also specified that by soil improvement between two tunnels, created tensile force in the crown of Aboozar tunnel will be reduced from 1266 KN to 840 KN