The magnetic relaxation in high-Tc superconductors YBa2Cu3O7 system prepared by modified melt-textured growth method was investigated. The relaxation rate, S, given by M-1dM/d log (t), is independent of magnetic field and temperature below a given temperature. T0, which is decreased with magnetic field. The pinning potential evaluated from the temperature-independent S is increased with temperature, but the potential is apparent. On the other hand, S in the range higher than T0 is increased with temperature. This gives the potential dependent on log (Jc).
