To figure out the force and deflection laws of the existing tunnel under the influence of tunneling underlying. The surrounding soil-free deformation induced by tunneling underneath could be obtained by Loganathan solution, then to simplify the existing tunnel as Euler-Bernoulli beam resisting on Vlazov foundation and take the tunnel lateral soil action on both sides of existing tunnel into consideration, then theoretical results of the existing tunnel deflection response can be extracted based on the condition of tunnel boundary and Taylor series. Compared with the measurements of engineering project from Shanghai city and centrifuge test, the solution given by the proposed method solutions is closer, and in turn security of the proposed method can be verified. By comparing with degraded result, the calculation result from the proposed method has more in line with measured data, then the influence of related parameters can be analyzed. The results show that: with increasing the vertical distance between new and old tunnels, the affection of the existing tunnel induced by tunneling underlying will be reduced. Enlarging the volume loss will cause the tunnel deformation and the bending moment increases linearly. Increasing the bending rigidity of the existing tunnel will obviously reduce the force and deflection response of the existing tunnel caused by tunneling underlying.