  We present the results of the neutron star X-ray binary system Cen X-3
performed by $Insight$-HXMT with two observations during 2017 and 2018. During
these two observations, the source reached a X-ray luminosity of $\sim 10^{38}$
erg s$^{-1}$ from 2 -- 105 keV. The analysis of the broadband X-ray spectrum
reports the presence of two cyclotron resonance scattering features (CRSFs)
with the fundamental line at $\sim$ 28 keV and the harmonic line at $\sim 47 $
keV. The multiple lines exist by fittings with different continuum models, like
the absorbed NPEX model and a power-law with high energy exponential cutoff
model. This is the first time that both fundamental and harmonic lines are
detected in Cen X-3. We also show evidence of two cyclotron lines in the
phase-resolved spectrum of Cen X-3. The CRSF and continuum spectral parameters
show evolution with the pulse profile, and the two line centroid energy ratio
does not change significantly and locates in a narrow value range of $1.6-1.7$
over the pulse phase. The implications of the discovering two cyclotron
absorption features and phase-resolved spectral properties are discussed.
