To solve the problem that the underground traverse network layout of metro tunnels is susceptible to side-folding light, difficult to use control points, and large lateral breakthrough errors, a new method for metro tunnel control measurement based on a space-free station continuous transmission method is proposed. A robust estimation theory and variance component estimation theory are added to the free-station’s three-dimensional coordinate compound iteration and high-precision weighting. The IGGIII weight function is used to derive an indirect adjustment mathematical model of the free station of the Helmert space in the subway tunnel and a strict formula of the linearized error equation. A ground 1︰1 simulation test shows that the mathematical model of the proposed method can reasonably determine the weight ratio of the three types of observations. At the same time, the model can resist the influence of the gross error of the data points affected by the construction environment on the solution results. When compared with the entire wire mesh, crosswire mesh, and prismatic wire mesh, the results show that the new method has high lateral breakthrough precision and good graphic strength, and is more effective and practical than the metro tunnel internal control measurement method. Thus, this new method has been promoted and applied in the section tunnel project from Zhangbasi Road Station to Zhangbayi Road Station of Xi’an Metro Line 6.