We have studied the irreversibility line and pinning potential U0 of high-Tc melt-textured YBa2Cu3O7-δ samples and found that the irreversibility line takes an exponential form B*-e(-T/Tc) over the temperature range of 72-85K, whereas the corresponding magnetic measurement at 77K gave a nonvanishing critical current density It is shown in the present paper that the functional expression of irreversibility line and pinning potential U0 of samples are closely associated.