  As a basic characteristic of cosmic ray (CR) propagation, the diffusive halo
can advance our understanding of many CR-related studies and indirect dark
matter. The method to derive the halo size usually has degeneracy problems thus
affected by large uncertainties. The diffusion gamma ray from high-latitude
clouds might shed light on the halo size independently. Since the spatially
dependent propagation (SDP) model has a better agreement with the observed CRs,
compared with conventional propagation model, in this work, we investigate the
halo thickness based on SDP model with Fermi-LAT $\rm\gamma$-ray observation on
the high- and intermediate-velocity clouds. As a result, in order not to exceed
the relative $\gamma$-ray emissivity in the high-latitude clouds, halo
thickness should be in the range of $\rm ~3.3\sim9~ kpc$. Moreover, the spatial
morphology of $\rm\gamma$-rays estimated based on SDP model under different
values of halo thickness are distinctive, which provides us a tool to determine
the halo size. We hope that our model could be tested and tuned by
multi-wavelength observations in the future.
