In order to solve the dust problem caused by coal accumulation in the coal yard, a novel environmentally-friendly polymer dust suppressant was synthesized by graft copolymerization using sodium alginate (SA) and sodium carboxymethyl cellulose (CMC) as raw materials. Single factor experiments were carried out to determine the optimal synthesis conditions of SA-CMC, taking the viscosity and surface tension as the performance indicators. Under the optimal formulation, the viscosity was 80 mPa·s and the surface tension was 36.541 mN/m. Aiming to optimize the wetting property and resistance to evaporation of SA-CMC, the SA-CMC was combined with the water retention agent CMCS and the surfactant SDBS to obtain the composite dust suppressant (SA-CMC/CMCS). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to analyze the reaction process. Scanning electron microscope (SEM) was used to characterize the micro-structures of the cured layer on the coal dust surface after the dust suppressant spraying. The product performance test results showed that the dust suppressant had the characteristics of water absorption and water retention. The dust suppressant was sprayed on the surface of the coal dust to form a cured layer with high compressive strength, the bearing pressure of the cured layer was 43 N, and the dust suppression rate was as high as 99% under the strong wind (12 m/s) erosion conditions. Compared with water, the dust suppressant prepared in this paper has a better protection effect on coal dust and other forms of dust.