  Time-series, multi-color photometry and high-resolution spectra of the short
period eclipsing binary V Tri were obtained by observations. The completely
covered light and radial velocity curves of the binary system are presented.
All times of light minima derived from both photoelectric and CCD photometry
were used to calculate the orbital period and new ephemerides of the eclipsing
system. The analysis of $O-C$ diagram reveals that the orbital period is
$0.58520481\ days$, decreasing at a rate of $dP/dt=-7.80\times10^{-8} d\
yr^{-1} $. The mass transfer between the two components and the light
time-travel effect due to a third body could be used to explain the period
decrease. However, a semidetached configuration with the less-mass component
filling and the primary nearly filling each of their Roche lobes was derived
from the synthesis of the light and radial velocity curves by using the 2015
version of the Wilson-Devinney code. We consider the period decrease to be the
nonconservative mass transfer from the secondary component to the primary and
the mass loss of the system, which was thought to be an EB type while it should
be an EA type (semi-detached Algol-type) from our study. The masses, radii and
luminosities of the primary and secondary are $1.60\pm0.07 M_\odot$,
$1.64\pm0.02 R_\odot$, $14.14\pm0.73 L_\odot$ and $0.74\pm0.02 M_\odot$,
$1.23\pm0.02 R_\odot$, $1.65\pm0.05 L_\odot$, respectively.
