High-field magnet application is one of most driving forces for the development of high temperature superconducting (HTS) materials. Recently, the magnet consisting of ReBa₂Cu₃O_7-δ based coated conductors (RE123, also called as secondary-generation high-temperature superconducting tapes, 2G-HTS) has exhibited the magnetic field as high as 26.4 T, over than the limit of conventional NbTi-Nb₃Sn magnets. As well, an overall superconductor magnet consisting of a 2G-HTS magnet inserted into the background with low temperature superconducting magnetic field of 17 T gave rise to the magnetic field up to 32 T, reaching a new world record with regard of all superconductor magnets. In reality, these breakouts take place thanks to the latest advances in practical HTS materials, showing the promising future for power applications. The great advantages and promising prospects of RE123 coated conductors over than other practical superconducting materials have spurred the related researches and rapid development of this field worldwide recently. The further development, however, will depend on the fundamental properties, producing yield, and optimum performance/price etc. In the present paper we give a brief introduction to RE123 coated conductor and its typical structure, as well as main technical routes for the scale-up preparation. We introduce the status and development for RE123 coated conductors around the world, including the existing research institutions and technologies they employed. In past decade, people have tested a variety of thin film techniques to realize the biaxial textured RE123 coated conductors epitaxially grown on flexible metallic tapes. For the most institutions working on the preparation of RE123 coated conductor, both IBAD and RABiTS have been used as popular technical routes due to their availability of long textured substrates, the feasibility of controlled buffer growth and the potential for cost-effective processing. At the same time, various thin film coating techniques including sputtering, pulse laser deposition (PLD), metallorganic chemical vapor or solution depositions (MOCVD, MOD) are employed to prepare the coated conductors for both buffer layers and superconducting layers. Particularly, some emerged MOD technologies for preparing superconducting layer with organic addition into the precursor solution or reduced fluorine content precursor solution have been addressed, due to their great potential for a cost-effective and rapid technical route to prepare RE123 coated conductor. It is also demonstrated that the considerable efforts for artificial flux pinning in RE123 coated conductor by introducing nanoparticles and substrate surface decoration have effectively improved the J_c value of RE123 under applied magnet field. The thickness effect of 2G-HTS is also an important issue, because in most case the critical current density would decrease while the thickness of superconducting layer increases. Such an effect may be suppressed with controlled techniques and microstructures or compositions. The coated conductors may maintain good biaxial texture as the thickness of superconducting layer increase from 1 to 5 μm, leading to huge increase in current-carrying capability of resultant 2G-HTS tape. It is believed that the mechanical properties of 2G-HTS tape are better than 1G-HTS tape, which is very important during the magnet coil winding. Excessive stress relief or Lorentz force would make coils split or deformed. To improve the anisotropy and mechanical properties, people have designed various types of practical conductors with RE123 tape stacks or metal tubes covered. Moreover, the welding technique of 2G-HTS tape is investigated due to importance on improving the usage rate of short tapes. In summary, the present review introduces the state of the art of 2G-HTS tape and relevant key science and technical issues, including the technical routes, artificial flux pinning, field dependence and thickness induced degradation of critical current density, joint technologies, as well as power applications, especially in the field of HTS magnet.

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