  A set of uniform carbon microspheres (CS) whose diameters have the order of $
0.125 \mu m$ to $10 \mu m $ was prepared from aqueous sucrose solution by means
of hydrothermal carbonization of sugar molecules. A pressed pellet was composed
by mixing CSs with polyethylene oxide (PEO). Electrical characterization of the
pellet was carried out showing Ohmic current-voltage characteristics and
temperature-dependent conductivity in the range $ 80K < T < 300K.$ The
conductivity reached a maximum value of $ 0.245 S/cm $ at $ 258K. $ The
dependence of conductivity on temperature was theoretically analyzed to
determine predominating mechanisms of electron transport. It was shown that
thermally-induced electron tunneling between adjacent spheres may take on an
important part in the electron transport through the CS/PEO composites.
