A great number ofundengound rock projects are maintained in the rock mass which is subject to rock darnage and fallure developmen. In many cases, the rock engineering is still under normal wohan conditons even though rock is already falls to some extent. This paper introduces tWo dbo concepts: rock fallure and rock engineering failure. Rock failure is dehoed as a mechedcal state under which an applicable charateristic is changed or lost.However, the rock engineering failure is an enginetw stae under which an applicable function is changed or lost. The fallure of surmunding rocks is the major reason of rock engineering failure. The criterion of rock enginetw failure depends on the lind of applicable functions. The rock engineering fallure state possesses a corresponding point in rock failure state. In this paper, a description of rock engineering failure criterion is glven by simply using a mechedcal equation or expression. It is expected that the study of rock engineering failure criterion will be an optimal approach that combines research of rock mechanics with rock engineering problems A great number ofundengound rock projects are maintained in the rock mass which is subject to rock darnage and fallure developmen. In many cases, the rock engineering is still under normal wohan conditons even though rock is already falls to some extent. This paper introduces tWo dbo rockfall is dehoed as a mechedcal state under which an applicable charateristic is changed or lost. surmount rocks is the major reason of rock engineering failure. The criterion of rock enginetw failure depends on the lind of applicable functions. The rock engineering fallure state possesses a corresponding point in rock failure state. In this paper, a description of rock engineering failure criterion is glven by simply using a mechedcal equation or expression. It is expected that the study of rock engineering failure crite rion will be an optimal approach that combines research of rock mechanics with rock engineering problems