A non-equilibrium ensemble is formulated and the partition function of a sy
stem in non-equilibrium transient state is derived by a method based upon t
he maximization of the Boltzmann's entropy constrained by non linear Boltzm
ann kinetic equation. We consider a logical theorem which expresses that th
e characteristic function in a non-equilibrium ensemble has a form similar
to the equilibrium one. The connection between the N-particle to one-partic
le non-equilibrium partition function is obtained and the time dependent th
ermodynamic functions as well as transport kinetic coefficients can then be
calculated.