The diffusive halo is a basic characteristic of cosmic ray(CR)propagation and can advance our under-standing of many CR-related phenomena and indirect dark matter.The method used to derive the halo size often has degeneracy problems and is thus affected by large uncertainties.The diffuse y rays from high-latitude clouds might shed light on the halo size independently.Because predictions using the spatially dependent propagation(SDP)mod-el have better agreement with the observed CRs than those of the conventional propagation model,in this work,we investigated halo thickness based on the SDP model using Fermi-LAT γ-ray observations of high-and intermediate-velocity clouds.We found that to avoid exceeding the relative y-ray emissivity in high-latitude clouds,the halo thickness should be in the range of 3.3-9 kpc.Moreover,the spatial morphology of y-rays estimated based on the SDP model for different values of the halo thickness are distinctive,which provides us with a tool to determine the halo size.This newly developed model can be tested and tuned using multi-wavelength observations in future stud-ies.