天文和宇宙学观测表明暗物质(DM)在宇宙中占据85%的物质成分，但目前我们只确定暗物质与普通物质的引力相互作用，对其本质，我们还一无所知。暗物质有很多种候选者，在粒子物理中，暗物质候选者来自于超出标准模型的新物理。本报告主要研究轻暗物质的理论模型和探测手段，主要内容分为三个部分：1. 我们提出了一种新的三体非弹性散射策略，使其应用在直接探测中并探测亚兆电子伏特(MeV)的DM。此过程的典型特征是近似单色谱的脉冲信号，其中反冲能来自于暗物质结合能或者消耗的DM粒子。2. 我们研究了被宇宙线助推的宇宙背景中微子(CNB)、亚MeV暗物质、超轻暗物质的能谱，并根据介电响应计算了助推的粒子与等离子激元之间的事例率，其中考虑了凝聚态靶物质的介质内部屏蔽效应。3. 我们用暗物质偶极矩研究了与重子的软散射，并探讨了宇宙线和星际电离气体对暗物质子晕结构蒸发的影响。最后，对主要结论作了总结。

Astrophysical and cosmological observation indicate the dark matter (DM) accounts for 85% ~of matter in the Universe. However, the only thing we confirm is its gravitational effect between DM and ordinary matter, and the nature of this substance remains unknown. There are many kinds of candidates for DM. In particle physics, a DM candidate particle can emerge from the new physics beyond the Standard Model (SM). This report mainly focus on theory model and detection method of light dark matter. The main text can be divided into three parts: 1. We present a new direct detection strategy for sub-MeV DM via the three-body inelastic scattering process. The typical signature from this process is almost a monoenergetic pulse signal where the recoil energy comes from either the binding energy or the consumed DM particle. 2. We consider these spectrum of the cosmic background neutrino, sub-MeV and super-light dark matter boosted by cosmic rays, and calculate corrdsponding event rate of the boosted particle-plasmon scattering in term of the dielectric response, which accounts for in-medium screening effect of a condensed matter target. 3. We consider dark matter soft-scattering on baryons via dipole moment interaction and explore the subhalo evaporation effect by interstellar ionization gas and accelerated cosmic rays. Finally we summarize our main conclusion.