  The Yang-Lee edge singularity is an intriguing critical phenomenon
characterized by nonunitary field theory. However, its experimental realization
for interacting many-body systems remains elusive. We show that Yang-Lee edge
singularities, regarded as many-body exceptional points, can be observed using
both the self-normal and the associated-biorthogonal Loschmidt echoes,
leveraging the advantages of nonunitary dynamics in non-Hermitian systems. The
Loschmidt echoes are demonstrated to display unitary dynamics in the
$\mathcal{PT}$-symmetric regime but exhibit nonunitary dynamics in the
$\mathcal{PT}$ symmetry-broken regime, leading to a sharp change near an
exceptional point. We hereby identify exceptional points in both the
non-Hermitian transverse field Ising model and the Yang-Lee model, and
determine the critical exponent that is consistent with nonunitary conformal
field theory. This work provides a direct observation of Yang-Lee edge
singularities in non-Hermitian many-body systems arising from nonunitary
dynamics.
