The method of exact evaluation of quantum partition function (QPF) in some four fermion models is proposed. The calculations are carried out by the path integral method. The integral is evaluated by introducing the additional fields (called Hubbard-Stratanovich transformation in some models), integration over fermionic variables, and considering the finite-dimensional approximation of the rest integral over bosonic fields in the infinite limit. The non-standard representation of propagator is proposed for the Fermi-theory of four-fermion interaction. This representation seems to be more convenient for the nonperturbative analysis. (author). 7 refs.