Abstract: The Large High Altitude Air Shower Observatory (LHAASO) stands as one of the largest experimental setups in the last 110 years dedicated to cosmic ray research. Its core scientific objective is to uncover the origins of cosmic rays, not only by detecting ultra-high energy (UHE) gamma-ray sources but also by accurately measuring the composition and energy spectrum of charged cosmic rays near Earth, and systematically studying the acceleration and propagation mechanisms of cosmic rays. From the identification of 12 UHE gamma-ray sources, marking the advent of UHE gamma astronomy, to the release of the first star catalog showcasing the diverse potential cosmic ray accelerators within the Milky Way, LHAASO has laid a solid foundation for uncovering the origin of cosmic rays. Moreover, these achievements have directed the subsequent research on cosmic ray acceleration and propagation, while also providing opportunities and challenges for testing existing theories and models. This article outlines the background of the LHAASO project, the significance of this major scientific instrument led by Chinese scientists in cosmic ray physics, and envisages its future research directions.