  We present a novel way of defining transmission coefficient of one spatial
dimensional few interacting electrons system. The formalism is based on the
probability interpretation of unitarity of physical scattering $S$-matrix. The
relation of our formalism to the well-established method for describing the
conducting properties of non-interacting systems, Landauer-B\"uttiker formula,
is discussed. The transport properties of interacting two-electron system is
also discussed as a specific example of our formalism.
