  We present and analyze the optical photometric and spectroscopic data of the
Be/X-ray binary MXB 0656-072 from 2006 to 2009. A 101.2-day orbital period is
found, for the first time, from the present public X-ray data(Swift/BAT and
RXTE/ASM). The anti-correlation between the H$\alpha$ emission and the $UBV$
brightness of MXB 0656$-$072 during our 2007 observations indicates that a mass
ejection event took place in the system. After the mass ejection, a low-density
region might develop around the Oe star. With the outward motion of the
circumstellar disk, the outer part of the disk interacted with the neutron star
around its periastron passage and a series of the X-ray outbursts were
triggered between MJD 54350 and MJD 54850. The PCA--HEXTE spectra during the
2007-2008 X-ray outbursts could be well fitted by a cut-off power law with low
energy absorption, together with an iron line around 6.4 keV, and a broad
cyclotron resonance feature around 30 keV. The same variability of the soft and
hard X-ray colors in 2.3-21 keV indicated that there were no overall changes in
the spectral shape during the X-ray outbursts, which might be only connected
with the changes of the mass-accretion rate onto the neutron star.
