  The young binary system HD 350731 is a noteworthy laboratory for studying
early-type binaries with similar components. We present here the analysis of
differential multi-color photometric and spectroscopic observations for the
double-lined detached system. Accurate absolute parameters were determined from
the simultaneous solution of light and radial velocity curves for the first
time. HD 350731 consists of two B8V-type components having masses and radii
respectively of $M_{1}=2.91\pm0.13$ M$_{\odot}$, $M_{2}=2.80\pm0.14$
M$_{\odot}$, $R_{1}= 2.11 \pm0.05$ R$_{\odot}$ and $R_{2}=2.07\pm0.05$
R$_{\odot}$. The effective temperatures were determined based on analysis of
disentangled spectra of the components and derived to be $12000\pm250$ K and
$11830\pm300$ K for the primary and secondary components, respectively. The
measured projected rotational velocities, 69.2$\pm$1.5 km s$^{-1}$ for primary
and 70.1$\pm$1.7 km s$^{-1}$ for secondary, were found closer to the
pseudo-synchronous velocities of the components. Comparison with evolutionary
models suggests an age of 120$\pm$35 Myr. Kinematic analysis of the unevolved
binary system HD 350731 revealed that it belongs to the young thin-disc
population of the Galaxy.
