One of the most important goals in the physics programs of the Energy Frontier research is to discover hints for extensions of the Standard Model of the particle physics. The High-Luminosity Large Hadron Collider (HL-LHC) will start the operation in 2026 to sustain and extend the physics sensitivity in the new physics search at the LHC. The HL-LHC will be realized by a full upgrade of the components of the LHC accelerator complex, such as the injector chain, the collimators, and the elements in the insertion regions for the experiments. Together with the upgrade of the LHC accelerator complex, the experimental detectors will be upgraded to cope with the high luminosity environment. The ATLAS experiment at the LHC will introduce new detectors, electronics, and trigger components to sustain the high performance of the reconstruction of the proton-proton collision events. There are two classes of the major challenges in the LHC-ATLAS upgrade projects; (1) development of a new pileup robust detector system which can distinguish interesting events from the other simultaneous proton-proton collisions, and (2) development of a new Trigger and Data Acquisition system to sustain the stability of the data-taking and flexibility of the online selection criteria in the trigger system during the HL-LHC operation.