The high-$T_c$ granular superconductor $YBa_2Cu_3O_{7-x}$ prepared by solid state reaction methods is studied in terms of higher order harmonics. The experimental variables for measurements of $χ_n$ were the sample temperature, the ac magnetic field amplitude $H_{ac}$ and the superimposed dc magnetic field $H_{dc}$. The harmonics were measured for magnetic field upto 8-th harmonics and temperature upto 3-rd harmonics. The results are compared with the calculated results using modified critical state model proposed by Y. Kim, et al. for fields ≤ 40 Oe. The magnetic field dependence of harmonics at 77K is well explained by this model with properly chosen fitting parameters for best fitting.
