  The recently discovered superconductivity with critical temperature $T_c$ up
to 80 K in the double-layer Nickelate La$_3$Ni$_2$O$_{7-\delta}$ under pressure
has drawn great attention. Here we report the positive muon spin relaxation
($\mu^+$SR) study of polycrystalline La$_3$Ni$_2$O$_{6.92}$ under ambient
pressure. Zero-field $\mu^+$SR experiments reveal the existence of magnetic
order in La$_3$Ni$_2$O$_{6.92}$ with $T_{N}=154\ \rm{K}$. The weak transverse
field $\mu^+$SR measurements confirms the bulk nature of magnetism. In
addition, a small quantity of oxygen deficiencies can greatly broaden the
internal magnetic field distribution sensed by muons.
