This paper aims to improve the adsorption capacity and decolorization rate of sodium alginate microspheres. Sodium alginate microspheres were prepared by blending polyvinyl alcohol and zeolite with sodium alginate as raw materials. On this basis, KSPZ (KCl-SA-PVA-zeolite microsphere) microspheres were modified by KCl. The optimal adsorption conditions were obtained by single factor test, and the samples were characterized before and after adsorption and the adsorption mechanism was explored. The results showed that the optimal adsorption conditions of KSPZ were as follows:pH 9, adsorption amount 1 g/L, adsorption time 6 h, initial mass concentration of MB (Methylene blue) 500 mg/L, adsorption capacity 426.63 mg/g, decolorization rate 85.33%. SEM showed that MB was successfully adsorbed on SPZ surface. FTIR showed that there were hydrogen bonds and electrostatic interactions between KSPZ and MB. The adsorption process followed quasi-second-order kinetics and Langmuir isothermal adsorption model, which indicated that the adsorption process was physical diffusion accompanied by chemical adsorption. KSPZ is an adsorbent with good stability and high decolorization rate, which provides guidance for the application of sodium alginate composite materials in the treatment of dye wastewater.