Abstract: Nanogels are nano-scaled three-dimensional networks, generally with good hydrophilicity and structural stability. As a natural macromolecular polysaccharide, chitosan has a great number of advantages such as non-toxicity and good biodegradability which has aroused wide attention. In this paper, with chitosan (CS) as the main building block, the free radical graft copolymerization is initiated at the hydroxyl carbon of chitosan and the nano-scaled aggregates are induced by the self-assembly of the hydrophobic poly(methyl acrylate) (PMA) graft chains. By introducing the redox-responsive cross-linker diallyl disulfide (DADS), the structure is locked and the tumor sensitive chitosan-poly(methyl acrylate) (CS-PMA) nanogels are obtained at high efficiency. This strategy is named as graft copolymerization induced self-assembly (GPISA). The size, morphology and structure of the nanogels are characterized by transmission electron microscopy (TEM), dynamic laser light scattering (DLS), FT-IR. The size of the nanogels can be controlled via adjusting synthetic parameters. Moreover, the nanogels can be modified with near infrared (NIR) fluorescence molecules-Cy5.5-NHS ester and magnetic resonance imaging (MRI) enhancement molecules-Gd-DTPA, leading to fluorescent/MRI dual-functional nanogels. Characterization results of MRI and fluorescence imaging demonstrate that the nanogels show great cell-labelling capability. The cell toxicity study by MTT assay confirm the low cytotoxicity of the nanogels to lymphatic endothelial cells (LECs) and breast cancer cells (MCF-7). All these results indicate that the bio-functional nanogels have great potential as NIR/MRI probe for the diagnosis and therapy of tumor.