Taking a highway tunnel as an example, based on the monitoring data of initial support and secondary lining strain in the field, the concept of strain ratio is introduced into the load sharing ratio of the support structure. The time-course variation law of support strain and the load sharing ratio of the monitoring section are studied. The strain data of secondary lining monitoring and load-structure model are compared to verify the reliability of the simulation. The numerical results of simulated internal forces under different load sharing ratios of secondary lining are extracted to calculate the safety factor of secondary lining, which reflects the construction stability from the side. The results show that the support strain is divided into three stages: rapid development (0 d-40 d), slow development to stability (40 d-160 d), and stability (60 d-360 d). The load sharing ratios of initial support and secondary lining calculated by introducing strain ratio are 31% and 69% respectively. The actual strain of secondary lining is consistent with the simulation trend. The peak value and the minimum value are located at the arch foot and side wall respectively, and the error range is 2.4%-8.5%, which verifies the certain reliability of the simulation. The peak value of secondary lining pressure is located at the arch foot, and the peak values of positive and negative bending moments are located at the top and arch foot respectively. Due to the sign reversal of bending moment at the arch foot, the arch foot is regarded as a dangerous node. The safety factor of secondary lining is higher than the critical value of safety factor, and the tensile safety factor of arch foot is close to the critical value. Due to the increase of load sharing ratio of secondary lining, the corresponding axial force and bending moment borne by secondary lining will increase, and the safety shows a downward trend.