The problem of modern deep karst is obvious with the development of engineering construction which brings up a series of geology engineering problems to the construction of tunnel. For example, the problem of high pressure water gushing and mud outburst in the construction of great deep buried Yuanliangshan tunnel in Yuhuai railway, which is a challenging problem in the theory, controlled the construction difficulty. The research actuality on relative conception, development type, characteristics and form mechanism of the modern deep Karst is also discussed in this paper which sketched the research keystone of the modern deep Karst including the research on conception, engineering geology classification and characteristics, controlling factors, development mechanism and evolvement, controlling on the tunnel construction of the modern deep Karst, and so on.