In the world scientific literature numerous investigations on development of fracture criteria of brittle and quasibrittle materials are carried out. At the same time the creep fracture or static fatigue problem for these materials is investigated not enough. To solve this problem the conception of damage and fracture of KachanovRabotnov is applied. It was taken into account, that imperfectness and microinhomogeneity of brittle and quasibrittle materials have casual character and at formulation of creep fracture criterion the probability methods are applied. It is considered that the specimen made of the brittle and quasibrittle materials consists of elements with the different initial states of damage. Distinctions of the damaged state of elements are determined by such factors, as porosity, phase composition, presence of micropores and microcracks of different size and other. So the damage distribution in small microvolumes are considered as the random. The kinetic equation for development of damage parameters with the random initial size distribution is proposed. The time to fracture, i.e. achievement of critical size of one of damaged elements, can be also considered as random. Thus at formulation of the creep fracture criterion the statistical models, based on the hypothesis of weak link and on the Weibull’s distribution are applied.