Abstract: In order to clarify the mechanism of carbon nanomaterials in regulating plant growth, this paper reviews the research progress of typical carbon nanomaterials including carbon nanotubes, graphene and carbon quantum dots in plant growth regulation with a focus on analyzing the pathways and molecular physiological mechanisms through which carbon nanomaterials enter the plant body. Research showed that carbon nanomaterials mainly promote plant growth through three aspects: 1) Uptake and transport: these materials can enter the plant body through the root symplast/apoplast pathway or leaf stomata/cuticle, and their uptake efficiency is influenced by material size, surface charge and hydrophilicity/hydrophobicity, and they can pass through the cell membrane through endocytosis or direct diffusion. 2) Regulating gene expression: carbon nanomaterials significantly upregulate the expression of aquaporin genes (such as PIP family), cell division related genes, and stress resistance defense genes (such as SOS1, WRKY), thereby promoting water and nutrient absorption and cell proliferation. 3) Enhanced photosynthesis: after entering chloroplasts, these materials act as electron carriers to accelerate the electron transfer chain, increase enzyme activity of Rubisco, or broaden the spectral utilization of photosynthesis through light conversion characteristics (such as upconversion luminescence), significantly increasing crop biomass and yield. In addition, carbon nanomaterials also show significant effects in inducing plant resistance to drought, salt, and heavy metal stress. Carbon nanomaterials have great potential as new plant growth regulators, but their deep molecular interaction mechanisms with plants and environmental safety still need to be further elucidated. In the future, multi-omics joint analysis should be strengthened and a three-in-one evaluation system of “materials-plants-environment” should be constructed to achieve safe and efficient application in agricultural production.