The effects of nano-SiO2 on the rheology of viscoelastic solutions formed by the bio- degradable surfactant fatty acid methyl ester sulfonate (MES) were studied. The process of MES micelles transforming from sphere or rod to wormlike was investigated with the increase in NaCl concentration by rheological measurements. The increase in η0 on the introduction of SiO2 was explained by considering the increasingly entangled wormlike micelles that were formed due to the screening of the electrostatic interactions. The results of rheological measurements show that the system of MES /NaCl can transform into wormlike micelles. MES micelle solutions without SiO2 are linear viscoelastic fluids in accord with a Maxwell model having a single relaxation time. But there is a process with some distributions of the relaxation time for MES micelle solution with SiO2.