We have studied flux dynamics in Bi:2223/Ag tape prepared by the CTFF technique in the orientation of H//c axis. Irreversibility line (IL) of a Bi:2223/Ag tape has been determined from AC susceptibility and the DC magnetization technique based on FC and ZFC curves. We have observed that the irreversibility temperature determined from the AC susceptibility method locates at a higher temperature than that was determined from the DC magnetization method. This shift could be attributed to the viscous dissipation generated by the oscillation of flux lines. FC magnetization at 20 K and 30 K for the field range from 500 to 2500 Oe are the same and show a plateau implying the same amount of reversible magnetization due to the Meissner current. Remanent magnetization versus temperature curves, which give us information on the flux pinning mechanism of the vortices, are also presented.