  II UMa is a late F-type (F5) contact binary with a close-in tertiary and a
distant visual companion. According to the four-color ($B$ $V$ $R_c$ $I_c$)
light curves' solutions of II UMa, it is a high fill-out (f=$86.6\,\%$) and low
mass ratio ($q = 0.172$) contact binary system, which indicate that it is at
the late evolutionary stage of late-type tidal-locked binary stars. The mass of
the primary star and secondary one are calculated to be $M_1 = 1.99M_\odot$,
$M_2 = 0.34M_\odot$. The primary star has evolved from ZAMS, but it is still
before TAMS, and the secondary star is even more evolved. Considering the mass
ratio ($M_3/M_1 = 0.67$) obtained by spectroscopic observations, the mass of
the close-in tertiary is estimated to be $M_3 = 1.34M_\odot$. The period
variations of the binary system is investigated for the first time. According
to the observed-calculated ($O$-$C$) curve analysis, a continuous period
increase at a rate of $dP/dt=4.88\times{10^{-7}}day\cdot year^{-1}$ is
determined. It may be just a part of a cyclic period change, or the
combinational period change of a parabolic variation and a cyclic one. More
times of minimum light are needed to confirm this. The presence of the tertiary
component may play an important role in the formation and evolution of this
binary system by drawing angular momentum from the central system during the
pre-contact stage.
