We have successfully prepared mercury-based high-temperature superconductors of composition by means of the encapsulation and short-time annealing technique. By measuring the hysteresis loops, the critical current density is determined by using Bean's model. Scaling behaviours of the pinning-force density are discussed. By using the short-time annealing technique, the irreversibility line and the flux-pinning properties of the Hg-1223 specimen were enhanced by the introduction of more lattice defects, such as screw dislocations, intergrowth structures and stacking faults, into the Hg-1223 specimen. Furthermore, it is shown that the temperature dependence of the irreversibility line exhibits different features within two temperature regions. In the low-temperature region is proportional to , while in the high-temperature region is proportional to . The observed can be clarified by comparison with the theoretical model.