The green-liquid-silicon-insoluble (GLSI) was obtained through green liquor desilication via black liquor combustion process using NaAIO2, and MgSO4, as compound desilication agents in this study. The morphology, composition and properties of GLSI were studied. ICP and SEM-EDAX were used to determine the composition, and SEM was used to observe the morphology. Laser particle size analyzer and sedimentation method were used to measure the particle size distribution. precipitation volume and precipitation time to evaluate the precipitation performance of GLSIS. The results show that NaAIO2-MgSO4, compound desilication agent has a good desilication effect. The desilication rate can reach 86. 17% and the content of Si element in corresponding GLSIs is the highest 5. 82% at the molar ratio Si: Al Mg as 10.30. 4. The spherical bulk structure and flocculation of GLSIs are the most obvious, smaller GLSI particles being observed on the surface. The contents of Al and Mg elements in the green liquor are the lowest and the desilication rate is up to 85. 84% at the molar ratio of Si: Al Mg as 1 : 0.35 0.35, and the content of Si element in GLSIS is the same as that at the molar ratio Si: Al Mg as 1:0.3 0. 4. The average particle size of the corresponding GLSIS is mainly in the range of 3~70 μm and the largest is 39 pm, which elucidates that the precipitation performance is also good. The content of Al and Mg elements of the latter is higher than that of the former, so the molar ratio of Si: Al: Mg is determined as 1 : 0.35: 0.35. [ABSTRACT FROM AUTHOR]