Abstract: In this study, different concentrations of Linseed gum (LG) and Methylcellulose (MC) were mixed, and the effects of LG concentration on the properties of composite polysaccharide water foam were systematically analyzed. The microstructure, pore structure, thermal stability and mechanical properties of composite polysaccharide aerogel (MC-LG) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. The results showed that the viscosity of complex polysaccharide solution increased significantly with the increase of LG concentration (0.1wt%~0.5wt%), while the foam expansion rate first decreased and then increased, and reached the maximum value (7.59%) at 0.4wt%. Compared with pure MC water foam (76.40 μm), the bubble distribution of MC-0.4wt% LG water foam was more uniform, and the average size was reduced to 59.11 μm, and it still maintains good stability after 48 h storage. Scanning electron microscope and infrared spectrum analysis showed that hydrogen bond interaction was formed between MC and LG molecules, and MC-LG aerogel containing 0.4wt% LG presents a relatively uniform honeycomb porous structure. The results of mechanical properties showed that the Young's modulus of MC-0.4wt% LG aerogel reaches 0.0982 MPa, which was significantly higher than that of single MC aerogel (0.0288 MPa), and the yield strength and compressive strength are also significantly improved. To sum up, when the concentration of LG is 0.4wt%, MC-LG aerogel has uniform and compact pore structure, good thermal stability and excellent mechanical properties, and the overall performance is ideal. This study can provide technical reference for the application of high-performance polysaccharide-based aerogels in food and biomedicine.