The mechanical properties of the surrounding rock of soft rock tunnel and the stress of the lining structure are highly random and uncertain. The structural safety design method based on deterministic analysis could hardly reflect the complexity of soft rock tunnel engineering, while traditional reliability calculation theory does not give an explicit expression to the real function of underground structure composing the surrounding rock and support system, hence hindering the application of reliability calculation theory in tunnel engineering. In view of this, we present a reliability evaluation method for the collaborative bearing capacity of surrounding rock and lining structure by constructing an explicit expression of response surface according to the limit state function of bearing capacity in SL 279—2016 (Code for design of hydraulic tunnels) in the light of uniform design and reliability theory. The single factor random variables that affect the collaborative bearing characteristics are analyzed, and the major factors of reliability are identified. The present method is applied to a specific project and compared with the traditional reliability calculation method. Results manifest that the present method simplifies the calculation, boosts accuracy and efficiency, and is well adaptive and feasible.