  G349.7 + 00.2 is a young Galactic supernova remnant (SNR) with a mushroom
morphology in radio and X-rays, and it has been detected across the entire
electromagnetic spectrum from radio to high energy $\gamma$-rays. Moreover, the
remnant is interacting with a molecular cloud based on the observations in the
radio and infrared band. The reason for the formation of the periphery and the
dynamical evolution of the remnant are investigated using 3D hydrodynamical
(HD) simulations. Under the assumption that the supernova ejecta is evolved in
the medium with a density gradient, the shell is composed of two hemispheres
with different radiuses, and the smaller hemisphere is in relatively dense
media. The resulting periphery of remnant is consistent with detected ones, and
it can be concluded that the peculiar periphery of G349.7+00.2 can be
reproduced as the remnants interacting with the medium with a density gradient.
