  MGRO J2019+37 within the Cygnus region is a bright and extended source
revealed by Milagro at 12-35 TeV. This source is almost as bright as Crab
Nebula in northern sky, while it is not confirmed by ARGO-YBJ around TeV. Up to
now, no obvious counterpart at low energy wavelengths has been found. Hence,
MGRO J2019+37 becomes mysterious and its VHE gamma-ray emission mechanism is
attractive. In this paper, a brief summary of the multi-wavelength observations
from Radio to gamma-ray is presented. All the available data from the
XMM-Newton and INTEGRAL at X-ray, and the Fermi-LAT at gamma-ray bands were
used to get constraint on its emission flux at low energy wavelengths. Then,
its possible counterparts and the VHE emission mechanism are discussed.
