银河系是可将其成员星解析为单体并通过分析大样本成员星的统计性质来理解其集成和演化历史的唯一星系，因此它是研究（盘）星系形成与演化的独特实验室。LAMOST巡天获得的上千万恒星光谱及Gaia巡天提供的精确恒星距离和自行为深入揭示银河系的结构、起源与演化提供了历史性机遇。项目拟结合LAMOST与Gaia得到的天区覆盖连续，在较大体积内统计完备且具有三维位置、三维速度以及年龄、质量、金属元素丰度等完整参数信息的恒星样本，精确描绘恒星数密度随年龄、质量、丰度、三维位置和三维速度的分布函数，开展：1）银河系（子）结构及其演化；2）银河系引力势与物质分布；3）银河系化学动力学性质及其演化；4）星际介质分布及其化学动力学性质等研究；揭示银河系的精细结构、物质组成与分布、恒星形成及化学动力学演化历史，理解星系并合、长期演化和恒星反馈等天体物理过程在银河系形成与演化历史中所起的作用，探究暗物质本质。

Understanding the formation and evolution of galaxies is a fundamental task of modern astronomy and astrophysics. Being a typical spiral galaxy, the Milky Way is a unique laboratory for the understanding of galaxy formation and evolution as it is the only galaxy that can be detailedly investigated star-by-star utilizing large samples of stars with information in full dimensionality — three dimensional position, three dimensional velocity, mass, age and chemical composition. The well-designed LAMOST Galactic Spectroscopic Surveys have delivered uniform stellar spectra and precise stellar parameters, including radial velocity, effective temperature, surface gravity, absolute magnitudes, metallicity and elemental (C, N, α-elements) abundances, for millions of stars using a simple yet non-trivial target selection function. This unprecedented database, combined with accurate parallaxes and proper motions from the ESA Gaia astrometric survey, provide a great opportunity to unravel the structure, origin and evolution of the Milky Way. Here we propose to characterize accurately the stellar distribution as a function of (3D) position, (3D) velocity, stellar age, mass, metallicity and element abundances, by making full use of the unique samples of LAMOST and Gaia that cover contiguous sky areas abd are statistically complete in a large volumes. With the stellar distribution function obtained, we plan to further study: 1) The Galactic (sub)structure and evolution; 2) The Galactic gravitational potential and matter/dark matter distribution; 3) The chemodynamic properties of the Galaxy and evolution; 4) The distribution and chemodynamic properties of the interstellar medium. The studies will help unravel the (fine) structures, matter content and distribution, star formation and chemodynamic evolution history of our Milky Way in detail, and provide answers to the fundamental questions about the galaxy formation and evolution, including for instance, the roles the merge events and the secular evolution and stellar feedback processes have played in the Galactic assemblage and evolution history. The studies will also shed light on the nature of dark matter.