  We present multi-wavelength observations of a typical long duration GRB
120326A at $z=1.798$, including rapid observations using a submillimeter array
(SMA), and a comprehensive monitoring in X-ray and optical. The SMA observation
provided the fastest detection to date among seven submillimeter afterglows at
230 GHz. The prompt spectral analysis, using Swift and Suzaku yielded a
spectral peak energy of $E^{\rm src}_{\rm peak}=107.8^{+15.3}_{-15.3}$ keV and
equivalent isotropic energy of $E_{\rm iso}$ as $3.18^{+0.40}_{-0.32}\times
10^{52}$ erg. The temporal evolution and spectral properties in the optical
were consistent with the standard forward shock synchrotron with jet
collimation ($6^{\circ}.69\pm0^{\circ}.16$). The forward shock modeling using a
2D relativistic hydrodynamic jet simulation also determined the reasonable
burst explosion and the synchrotron radiation parameters for the optical
afterglow. The X-ray light curve showed no apparent jet break and the temporal
decay index relation between the X-ray and optical ($\alpha{\rm
o}-\alpha_{X}=-1.45\pm0.10$) indicated different radiation processes in the
X-ray and optical. Introducing synchrotron self-inverse Compton radiation from
reverse shock is a possible solution, and the detection and the slow decay of
the afterglow in submillimeter supports that this is a plausible idea. The
observed temporal evolution and spectral properties as well as forward shock
modeling parameters, enabled to determine reasonable functions to describe the
afterglow properties. Because half of events share similar properties in the
X-ray and optical to the current event, GRB120326A will be a benchmarks with
further rapid follow-ups, using submillimeter instruments such as SMA and ALMA.
