Cellulose nanofibers (CNFs) have often been added into aerogels for improving the mechanical robustness [1].The insolubility of CNFs in solvent, however, is a main problem in the composite process.Phase separation usually occurs due to the low solubility of interconnected structures formed in polymethylsilsesquioxane (PMSQ) gels by using methyltrimethoxysilane (MTMS) as monomer [2].We have fabricated PMSQ-CNFs aerogels by using dimethyl sulfoxide (DMSO) as solvent to suppress phase separation [3].In this paper, our work focuses on the experimental investigation by adjusting the relationship between phase separation and gelation in DMSO as solvent in order to fabricate uniform PMSQ-CNFs aerogels.CNFs were extracted by the acid hydrolysis of cotton pulps in a 64 wt.% aqueous H2SO4 solution and then dispersed into silica sols under the help of DMSO.The PMSQ-CNFs aerogels were obtained by sol-gel method and supercritical drying.In the experiments, the sedimentations of CNFs and polymerized PMSQ gels particles in DMSO are observed.The morphologies of aerogels were obtained at different gelation time and phase separation time by changing the contents of DMSO.The dependence of gelation time and phase separation time on the amount of DMSO was discussed.The results show that DMSO is an effective solvent to disperse CNFs and dissolve polymerized gels particles.