In recent years, engineering accidents owing to the failure of tunnel support is become more and more, because the development of tunnel and underground space engineering is becoming to lager depth and lager length.. There are two key reasons, one is the surrounding rocks have obvious rheological properties, and the stability and reliability have obvious time properties, but there is no more study about the time-stability and time-reliability of the surrounding rocks and tunnel support, another is that there is no flawless risk assessing systems about tunnel engineering in our country, and it is short of forecasting risks, managing risks and assessing risks effectively. In this paper, combing with the Chinese National Natural Sciences Foundation which is the stability and reliability of the structure of tunnel and underground space, taking Fang Doushan digging engineering as an example, it studies the time reliability and risk management of the support of lager depth tunnel, the key contents have,(1) In the study of the engineering mechanical characters, it determines the Kelvin-voigt rheological model for surrounding rocks of Doushan tunnel through the uniaixal, triaxilitical and rheological experiments and curve fitting and analyzing results, and examining the feasibility of Kelvin-voigt rheological model.(2) Based on the Kelvin-voigt model, it deducts time-equations of the contacting pressure between support and surrounding rocks and displacement, and defines the time-failure-probability of tunnel support and calculating methods, i.e. the time-damaged probability is the ratio of the length of the arcs AB and OB, here, the length of the arc AB refers to the cross between displacement time -curve and the displacement special value to the displacement converging valve, the length of the arc OB refers to the effect point between surrounding rocks and the support to the displacement converging valve. Based on these, it determines the time reliability equation in tension and in pressure based on the model of "load and structure", and perform programs to study importantly the time reliability of tunnel support based on the model of "convergence and restriction".(3) Under the theoretical analysis guidance, it arranges six monitoring sections during lager depth roads to monitor importantly I steel stress, the contacting pressure between shotcrete and surrounding rocks, internal stress of shotcrete, axis-pressure of bolts, stress of the temporal steel, steel stress of the secondary linings, contacting