Abstract: The excavation of multi-arch tunnels with large chambers and spans leads to frequent load transfers and complex stress characteristics on the support structures, field testing allows for a more accurate study of the stress distribution characteristics of this support structure. This paper relies on the Changsha Guanyin Rock Unequal Span Four-Arch Tunnel project, we use strain gauge to monitored stress in typical sections during the entire construction process of the steel arches and secondary lining. Analyzing test results revealed that the main advance tunnel experienced greater surrounding rock pressure compared to subsequent tunnels. The excavation of the right main tunnel and the left and right auxiliary tunnels occurred later, resulting in fewer disturbances and smaller internal forces in the support structures. The overall distribution of internal forces in the steel arches displayed an asymmetrical pattern, with higher forces on the right side. The maximum axial pressure of 402.71 kN and maximum bending moment of 7.97 kN·m were observed at the right foot of the left main tunnel. The secondary lining exhibited low asymmetry, with only the left main tunnel showing significant asymmetrical distribution. The internal force disturbances in the left main tunnel's support structures were primarily influenced by the excavation of subsequent adjacent tunnels. During the excavation and support stages of the subsequent right main tunnel and left auxiliary tunnel, most positions in the left main tunnel experienced internal force increments exceeding half of the total increment. In summary, the construction plan of “first main and then auxiliary, left main first” is found to be reasonable, and the support structure meets the specification requirements. The research findings can provide references for the design and construction of multi-arch tunnels under complex conditions.