  In this paper, we made a statistical approach on the thermodynamic structure
of the nucleon and its quark distributions. We assume that the nucleon is a
thermodynamic system of quarks and gluons. After we derived the quark density
of states from the Dirac Equation, we calculated each quark's chemical
potential, associating it with the quark's spin distribution. By using the sum
rule of the longitudinal momentum, we obtain a function showing the relation
between the temperature, radius and mass of the nucleon. The nucleon's radius
is determined by the total energy minimal principle, and thus the temperature
is also known. Finally, we deduced the quark distribution functions near x=1,
and the results are in agreement with the experimental data.
